murmel-langref.lisp

;;;
;;; === Murmel Language Reference =====
;;;
;;; The file `murmel-langref.lisp`
;;; is an executable language reference manual
;;; for Murmel, a single-namespace Lisp dialect
;;; inspired by Common Lisp.
;;;
;;; See also Murmel's default library [Mlib](mlib.md) 
;;; which contains additional functions and macros.
;;;
;;; The file `murmel-langref.lisp` can be read as-is or run with:
;;;
;;;     $ java -jar jmurmel.jar --repl --echo < murmel-langref.lisp
;;;
;;; or transformed to Markdown:
;;;
;;;     $ sed -nf scripts/langref-to-md.sed murmel-langref.lisp \
;;;     > murmel-langref.md
;;;
;;; Murmel is WIP, please note the section
;;; [Known issues](#known-issues) at the end of this file.

;;; == Murmel Reference ===============

;;; - [S-expressions](#s-expressions)
;;; - [Comments](#comments)
;;; - [Predefined Symbols](#predefined-symbols)
;;; - [Basic Special Forms](#basic-special-forms)
;;; - [Function application](#function-application)
;;; - [Data types](#data-types)
;;; - [Reserved words](#reserved-words)
;;; - [Variables and scope](#variables-and-scope)
;;; - [Additional Special Forms](#additional-special-forms)
;;; - [Backquote - fill-in templates](#backquote)
;;; - [Basic Primitives](#basic-primitives)
;;; - [Logic, Predicates](#logic-predicates)
;;; - [Conses and lists](#conses-and-lists)
;;; - [Vectors, Sequences](#vectors-sequences)
;;; - [Hashtables](#hash-tables)
;;; - [I/O](#io)
;;; - [Misc](#misc)
;;; - [Time](#time)
;;; - [Predefined Numeric Primitives](#predefined-numeric-primitives)
;;; - [Predefined Graphics Primitives](#predefined-graphics-primitives)
;;; - [Java FFI](#java-ffi)
;;;
;;; Additional functions that can be loaded with `(require "mlib")`
;;; - [Mlib - Default library for Murmel](mlib.md)


;;; == Introduction ===================
;;;
;;; "Hello, World!" program written in Murmel:

(format t "Hello, World!")

;;; The program text above when run in the REPL should print the famous
;;;
;;;     Hello, World!
;;;
;;; followed by the result of `format`
;;;
;;;     ==> nil
;;;
;;; and the prompt `JMurmel>`.


;;; == S-expressions ==================
;;;
;;; Murmel is a Lisp dialect. As such the language isn't
;;; really defined in terms of program text but in terms
;;; of in-memory objects (lists, symbols and other atoms)
;;; that are acceptable to `eval`.
;;;
;;; That said, JMurmel's default reader turns S-expressions
;;; from the input stream into equivalent in-memory objects. So
;;; for this reference we'll use S-expressions to describe
;;; programs that are valid Murmel, i.e. are acceptable to `eval`.
;;;
;;; In this reference in-memory objects that are valid Murmel
;;; (as well as their textual representation as S-expressions)
;;; are referred to as "forms".
;;;
;;; The following are S-expressions that JMurmel's reader
;;; will accept and transform into in-memory objects.
;;; Valid S-expressions may or may not be "forms"
;;; (i.e. may or may not eval w/o error).

; = Atoms that are not symbols

1
1.0
"a string"
#\a   ; the character 'a'
#xff  ; the integer number 255 in hex


; = Single quote

; A single quote `'` is a shorthand for `(quote form)`,
; see [Basic special forms](#basic-special-forms).

'form


; = Atoms that are symbols

; Symbols usually start with a letter and are composed of
; letters, digits and dashes ('-'),
; but pretty much any token that is not another atom will be
; parsed as a symbol.
; Murmel handles symbols similar to Common Lisp,
; see "CLHS 2.3.4 Symbols as Tokens" http://clhs.lisp.se/Body/02_cd.htm
; for details.
;
; Examples:

'a-symbol
'|a symbol|
'a\ symbol
'123"345
'123.456.789


; = Conses (pairs) and lists

; A dotted pair

'(a . b)              ; ==> (a . b)

; A dotted list

'(a . (b . (c . d)))

; Shorthand for dotted list

'(a b c . d)

; A proper list

'(a . (b . (c . ()))) ; ==> (a b c)

; Shorthand for a proper list

'(a b c)              ; ==> (a b c)


; = Labeled subobjects

; Since: 1.4.6

'(a #1=b #1# c)       ; ==> (a b b c)

; Note that a label can only be used after it's value was completely read,
; i.e. `'#1=(a b . #1#) is an error in Murmel (while valid in CL).


; = Hashtables

; Since: 1.3.1

#H(eql k1 v1 k2 v2 k3 v3)


;;; == Comments =======================

; One line comments are started with `;`, i.e. everything between a semicolon
; and the end of the line is ignored:

;     ; this is a comment

; Multiline comments are started with `#|` and ended with `|#`:

#|
This is a
multiline comment.
|#

; The pair `#!` and `!#` can also be used for multiline comments.

;;; == Predefined Symbols =============

; = `nil` and `t`
; `nil` and `t` are pre-defined self-evaluating symbols.

nil ; ==> nil
t   ; ==> t

; Murmel treats the symbols `nil` and `t` the same way
; as Mr. Moon specified them in a Memo (see "The Evolution
; of Lisp pp 62"):
;
; > NIL is a symbol, the empty list, and the distinguished
; > "false" value. SYMBOLP, ATOM, and LISTP are true of it;
; > CONSP is not. CAR, CDR, and EVAL of NIL are NIL.
; > NIL may not be used as a function, nor as a variable.
; >
; > T is a symbol and the default "true" value used by predicates that
; > are not semi-predicates (i.e., that don’t return "meaningful" values
; > when they are true.) EVAL of T is T. T may not be used as a variable.
; > T is a keyword recognized by certain functions, such as FORMAT.


; = internal-time-units-per-second
; `internal-time-units-per-second` contains the resolution
; of the time related functions, see below.

internal-time-units-per-second ; ==> 1.0E9


; = pi
; `pi` contains the value of the mathematical constant pi
; in double precision.

pi ; ==> 3.141592653589793


; = \*command-line-argument-list\*
; `*command-line-argument-list*` contains all command line arguments
; to the Murmel program. Below example illustrates this:
;
;     C:\> java -jar jmurmel.jar -- a b c
;     ...
;     JMurmel> *command-line-argument-list*
;     
;     ==> ("a" "b" "c")
;     JMurmel>


; = array-dimension-limit
; Largest acceptable vector index.


; = most-positive-fixnum, most-negative-fixnum
; These global variables contain the smallest and largest fixnum value.


; = \*condition-handler\*
;
; Since: 1.4
;
; This variable can be set to a function of one parameter.
; If `*condition-handler*` is non-nil then it will be invoked in case of an error,
; the argument will be the condition describing the error.
; During invocation of the condition handler it will be disabled:
; if the current handler dynamically replaced a previous handler
; then the previous handler will be temporarily restored.


; = \*random-state\*
;
; Since: 1.4.4
;
; Will initially be `nil`. Will be lazily created by one-arg `random`
; or zero-arg `make-random-state`.
 

; = REPL variables
;     @-, @+, @++, @+++, @\*, @\*\*, @\*\*\*, @/, @//, @///
;
; These variables are only defined when using the REPL.
; They work similar to CL's REPL variables without the leading `@`.
;
; The global variables @\*, @\*\*, @\*\*\* are maintained by the Lisp read-eval-print loop
; to save the values of results that are printed each time through the loop.
;
; The value of @\* is the most recent primary value that was printed,
; the value of @\*\* is the previous value of @\*,
; and the value of @\*\*\* is the previous value of @\*\*.
;
; If several values are produced, @\* contains the first value only;
; @\* contains nil if zero values are produced.
;
; The values of @\*, @\*\*, and @\*\*\* are updated immediately prior to printing the return value
; of a top-level form by the Lisp read-eval-print loop.
; If the evaluation of such a form is aborted prior to its normal return,
; the values of @\*, @\*\*, and @\*\*\* are not updated.


;;; == Basic Special Forms ============

; = quote
;     (quote form) -> form
;
; `quote` returns a form without evaluating it.

(quote a-symbol) ; ==> a-symbol

; = lambda
;     (lambda (params*) forms*) -> closure
;
; When a lambda is created by the special form `lambda`
; then the lexical environment is captured at the time of lambda creation.
; Arguments to the special form `lambda` are not evaluated.

(lambda (p1 p2) p1)

; `lambda` with varargs:
; If paramlist is a symbol then all arguments will be
; packed into a list and bound to the symbol.
; If paramlist is a dotted list then remaining arguments
; will be bound to the last parameter.

(lambda popt (write popt)) ; no mandatory arguments
(lambda (p1 p2 . prest) (write prest)) ; two mandatory arguments


;;; == Data types =====================
;;;
;;; Murmel supports symbols and cons cells (and lists built from cons cells)
;;; as well as other atoms that are not symbols.
;;; These other atoms are double precision floating point numbers,
;;; integer numbers, vectors, strings, characters, bits and more.
;;; Custom primitives may support additional atoms.
;
; Murmel's type system (and JMurmel's corresponding host types) look like so:
;
;     ;; Murmel type                ; description or "Murmel form -> Java class used in JMurmel"
;
;     t
;
;        cons                       ; (cons 1 2)                     -> ConsCell
;
;        atom                       ; all Murmel objects except cons cells
;                                   ; and all Java Objects are atoms
;
;           symbol                  ; 'sym                           -> LambdaJSymbol
;              null                 ; nil                            -> null
;                                   ; nil is the only object of type null
;
;           number                  ; java.lang.Number is accepted for reading
;              float                ; 2.3                            -> java.lang.Double
;              integer              ; 42                             -> java.lang.Long
;                                   ; only 54 bits are used
;
;           character               ; #\A                            -> java.lang.Character
;
;           random-state            ; (make-random-state)            -> java.util.Random
;
;           vector                  ; (make-array NN t t)            -> java.util.ArrayList
;                                   ; (make-array NN t CC)           -> java.util.ArrayList
;                                   ; makes an ArrayList w/ size NN and initial capacity CC
;                                   ; java.util.List is acceptable for seqref and seqset
;              simple-vector        ; (make-array NN t nil)          -> Object[]
;                                   ; #(1 2 3)                       -> Object[]
;              string               ; (make-array NN 'character t)   -> java.lang.StringBuilder
;                                   ; java.lang.StringBuffer is acceptable for sref and sset
;                                   ; java.lang.CharSequence is accepted for sref
;                 simple-string     ; (make-array NN 'character nil) -> char[]
;                                   ; "abc"                          -> java.lang.String
;              bit-vector           ; (make-array NN 'bit t)         -> BitVector
;                 simple-bit-vector ; (make-array NN 'bit nil)       -> boolean[]
;                                   : #*0101                         -> boolean[]
;
;           hash-table              ; (make-hash-table [test [size]])
;                                   ; #H(eql one 1 two 2 three 3)     -> EqlMap
;                                   ; (make-hash-table ['eql [size]]) -> EqlMap
;                                   ; (make-hash-table ['equal [size]]) -> EqualMap
;                                   ; (make-hash-table 'eq [size])    -> java.util.IdentityHashMap
;                                   ; (make-hash-table 't [size])     -> java.util.HashMap
;                                   ; java.util.Map is acceptable for hashref, hashset, clrhash...
;
;           function                ; (lambda (param) param)         -> Closure or MurmelFunction
;
;           (list ::= cons | null)
;           (sequence ::= list | vector)
;
;
;     ;; Murmel's condition type hierarchy is a subset of CL's condition type hierarchy,
;     ;; `error` and subtypes are pretty much the same. Murmel doesn't have multiple
;     ;; inheritance, though, and `reader-error` only extends `stream-error`.
;     ;; JMurmel maps conditions to Java exceptions as best as possible.
;
;           condition                           java.lang.Throwable
;               error                           java.lang.Exception
;
;                 (murmel-error                 LambdaJError extends RuntimeException extends Exception)
;
;                                               ;;; extends LambdaJError
;                   simple-error                SimpleError extends LambdaJError
;
;                   cell-error                  CellError extends LambdaJError
;                       unbound-variable        UnboundVariable extends CellError extends LambdaJError
;                       undefined-function      UndefinedFunction extends CellError extends LambdaJError
;
;                   control-error               ControlError extends LambdaJError
;
;                   program-error               ProgramError extends LambdaJError
;
;                   parse-error                 SExpressionReader.ParseError extends LambdaJError
;
;
;                   arithmetic-error            java.lang.ArithmeticException extends RuntimeException
;                       (overflow, underflow)
;       
;                   type-error                  java.lang.ClassCastException extends RuntimeException
;                       simple-type-error       SimpleTypeError extends ClassCastException
;                       invalid-index-error     InvalidIndexError extends IndexOutOfBoundsException
;       
;                   file-error                  java.nio.file.InvalidPathException
;                                               extends IllegalArgumentException extends RuntimeException
;
;
;                   stream-error                java.io.IOException
;                       end-of-file             java.io.EOFException extends IOException
;                       reader-error            ReaderError extends IOException
;                                               NOTE:
;                                               CL's reader-error has two superclasses: stream-error and parse-error
;                                               if c was a reader-error then both
;                                               (typep c 'stream-error) and (typep c 'parse-error) are true

; The above is a subset of CLtL2's predefined data types,
; see "CLtL2 2. Data Types" https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node15.html
; Murmel's condition hierarchy is a subset of CLtL2 predefined condition types,
; see "CLtL2 29.5. Predefined Condition Types" https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node346.html
; and "CLHS 9.1.1 Condition Types" http://clhs.lisp.se/Body/09_aa.htm

; Murmel treats symbols case-insensitive.
; Symbol names are of arbitrary length, however only the
; first 30 chars are significant.
;
; Implementation note: JMurmel preserves the
; capitalization of the first encounter of a symbol
; for printing, e.g.:
;
;     '(AbC . dEf) -> (AbC . dEf)
;
; but
;
;     '(AbC . abc) -> (AbC . AbC)

'*a-sample-symbol*
'a\ symbol\ with\ spaces!

; Empty list, printed as `nil`

;     ()

; Shorthand for empty list

;     nil

; Tokens that consist of a sign or digit followed by digits
; are interpreted as integer numbers (java.lang.Long)

1

; Datatype float: a number in double precision
;
; numbers that contain the characters '.eE' are interpreted
; as floating point numbers (java.lang.Double)

1.0

; a float in scientific notation

1e3

; Stringliterals may have a maximum length of 2000 chars.
; Stringliterals of the same value are coalesced (interned).

"a string literal"
"another 'literal' \"string literal\""


;;; == Reserved words =================

; In addition to `nil` and `t` the symbols of the special forms are reserved, i.e.
; may not be used as a function nor as a variable:
;
;     nil, t,
;     lambda, quote, cond, labels, if, define, defun, let, let*, letrec, macrolet,
;     setq, progn, catch, thwrow, unwind-protect, try,
;     multiple-value-bind, multiple-value-call,
;     defmacro, declaim, load, require, provide


;;; == Variables and Scope ============

; Symbols are bound to global variables using `define` or `defun`
; (see below), and to local variables using `let, let*, letrec` or
; lambda parameter lists.
;
; Murmel's global bindings are lexical and must be defined before use,
; i.e. a symbol is bound to
; a newly created variable when define or defun are actually executed.
; The symbol's binding as well as the variable's extent (lifetime)
; last to the end of the program (the symbol's binding may be
; temporarily replaced by a local or dynamic binding, though).
;
; Murmel's local bindings are lexical, i.e. a symbol is bound to
; a newly created variable when a let/let\*/letrec/lambda form
; is evaluated. The symbol's binding as well as the associated variable
; are removed when leaving the lexical scope of the `let/let\*/letrec/lambda`
; form, restoring any previously existing binding (which may have
; been local or global).
; Except: `let* dynamic` will treat global symbols as "special", see below.


;;; == Additional Special Forms =======

;;; = (define symbol optional-object?) -> symbol
;
; `define` binds symbols in the global environment with
; memory locations that hold values.
; Murmel's `define` is somewhat similar to Common Lisp's `defparameter`
; except:
;
; CL's `defparameter` creates special global variables while
; Murmel's `define` creates global variables that can be
; lexically hidden by e.g. a let-binding.
;
; The first argument is not evaluated, the second one - if given - is.
; The second argument to `define` is optional and defaults to `nil`.

(define *global-var* 42)               ; ==> *gloval-var*
(define f1 (lambda (p1 p2) (+ p1 p2))) ; ==> f1

; `define` forms can appear inside toplevel `let, let*, letrec, multiple-value-bind` forms.

;;; = (defun symbol (params\*) docstring? forms\*) -> symbol
;
; `defun` is a shorthand for defining functions:
;
;     (defun symbol (params*) forms*)
;        <=>
;     (define symbol (lambda (params*) forms*))
;
; An optional docstring is ignored.
; Arguments to `defun` are not evaluated.

(defun f2 (p1 p2) (+ p1 p2)) ; ==> f2

; `defun` forms that appear inside toplevel `let, let*, letrec, multiple-value-bind` forms
; will bind a globally visible symbol to a closure (aka let-over-lambda):

(let ((counter 0))
  (defun pre-increment-counter ()
    (setq counter (1+ counter)))

  (defun pre-decrement-counter ()
    (setq counter (1- counter)))

  (defun peek-counter ()
    counter))

(pre-increment-counter)  ; ==> 1
(pre-increment-counter)  ; ==> 2
(pre-decrement-counter)  ; ==> 1
(peek-counter)  ; ==> 1

;;; = (defmacro name (params\*) docstring? forms\*) -> symbol<br/>(defmacro name) -> prev-name
;
; `defmacro` defines a macro, similar to CL's `defmacro`.
; Macros are somewhat similar to functions:
; On a function application the functions's arguments
; are eval'd and the result of the function will be used as is.
; On a macro application the macro's arguments are
; NOT eval'd, but the result of the macro is.
;
; IOW a function produces a value, a macro application
; produces code that will be eval'd.
; Macros are defined in a macro namespace.
; All macros are in the global scope, i.e. macros
; are not scoped but once defined they are visible everywhere.
;
; `(defmacro name)` can be used to unbind previously
; defined macros.
;
; An optional docstring is ignored.

(defmacro twice (arg) (list '* arg 2))  ; ==> twice
(twice 3) ; ==> 6.0
(defmacro twice) ; ==> twice; macro is unbound
(defmacro twice) ; ==> twice; no-op

;;; = (setq symbol value [more-symbols more-values]\*) -> last-value
;
; `setq` updates the value(s) of the given global or local symbol(s).
; In interpreted Murmel undefined variables will be created on the fly,
; in compiled mode variables must have been defined previously.

(define a nil)
(let ((b nil) (c nil))
  (setq a 1 b 2 c (+ a b))) ; ==> 3.0

;;; = (if condform form optionalform?) -> result

(if nil 'YASSS! 'OHNOOO!!!) ; ==> OHNOOO!!!

;;; = (progn forms\*) -> result

(if t (progn (write 'abc) (write 'def)))

;;; = (cond (condform forms\*)\* (t forms\*)?) -> result

;;; = (labels ((symbol (params\*) forms\*)\*) forms\*) -> result
;

;;; = (let optsymbol? ((symbol bindingform)\*) bodyforms\*) -> result
;
; Works similar to CL's `let` with the addition
; of Scheme's "named let".
; The let-bound variables `symbol` as well as `optsymbol` - if given -
; are bound inside bodyforms.
; `optsymbol` will be bound inside `bodyforms` to a lambda
; whose parameters are the let-variables and whose code is
; `bodyforms`. Therefore `optsymbol` can be used for
; recursive calls within `bodyforms`.

(let loop ((x 3)
           (msg "hi"))
  (if (= x 0)
      (write msg)
    (progn (write (floor x)) (loop (- x 1) msg))))

;;; = (let dynamic ((symbol bindingform)\*) bodyforms\*) -> result
;
; Similar to `let` except: globals are not shadowed but temporarily
; bound to the given value, and the previous value is restored when
; leaving the scope of the `let` form.
; I.e. `let dynamic` treats globals as "special".
;
; Example:

(setq a 1)
(define b 2)
(defun f () (write (cons a b)))

(f)
(let dynamic ((a 11) (b a))
  (f))
(f)
; will print `(1 . 2)(11 . 1)(1 . 2)`.

;;; = (let* optsymbol? ((symbol bindingform)\*) bodyforms\*) -> result
;
; Works like `let` (see above) with the addition:
; each `bindingform` "sees" the previous symbols. If multiple
; let-bindings use the same symbol the last one hides
; preceeding ones.

(let* loop ((y 10)
            (x (+ y 20))
            (x (floor (/ x 10)))
            (msg 'hi))
  (if (= x 0)
      (write msg)
    (progn (write (floor x)) (loop 0 0 (- x 1) msg))))

;;; = (let* dynamic ((symbol bindingform)\*) bodyforms\*) -> result
;
; Similar to `let*` except: globals are not shadowed but temporarily
; bound to the given value, and the previous value is restored when
; leaving the scope of the `let*` form.
; I.e. `let* dynamic` treats globals as "special".

(define *g* 'global)
(defun fun () (write *g*))
(let* dynamic ((*g* 'temp)) (fun)) ; fun will write temp
*g* ; ==> 'global

;;; = (letrec optsybol? ((symbol bindingform)\*) bodyforms\*) -> result
;
; `letrec` works like `let` and `let*` except each bindingform "sees"
; all other let symbols as well as it's own symbol.
; All symbols are bound, but only the preceeding bindings
; are defined (have a value) while eval'ing the `bindingform`.
; That way a let-bound variable could be a recursive lambda.

(letrec ((x 1) (y (+ x 1))) (write y))


;;; = (macrolet ((symbol params docstring? forms)\*) forms\*) -> result
;
; Since: 1.4.7
;
; `macrolet` defines local macros and executes `forms` using the local definitions.
; It is an error to shadow local macros with a local function (see `labels`)
; or with a named-let loop label.
; A docstring if given will be ignored.


;;; = (catch tagform forms\*) -> result
;
; Since: 1.3
;
; `catch` is used as the destination of a non-local control transfer by `throw`.


;;; = (throw tagform resultform) -> |
;
; Since: 1.3
;
; `throw` causes a non-local control transfer to a `catch` whose tag is `eq` to tag.
; TODO: If there is no outstanding catch tag that matches the throw tag,
; no unwinding of the stack is performed, and an error of type control-error is signaled.


;;; = (unwind-protect protected-form cleanupforms\*) -> result
;
; Since: 1.3
;
; `unwind-protect` evaluates `protected-form` and guarantees that `cleanup-forms`
; are executed before unwind-protect exits, whether it terminates normally or is aborted
; by a control transfer of some kind.


;;; = (try protected-form . error-obj) -> result
;
; Since 1.4
;
; `try` evaluates `protected-form`. If no error occurred during evaluation then
; the values from `protected-form` are the final result.
; If an error occurs then `try` returns the `error-obj` if given or null as the primary result,
; the secondary result is the condition.
;
; Example:
;
;     (multiple-value-bind (result condition)
;       (try (1+ most-positive-fixnum) 'error)
;       (if (eq result 'error)
;             (progn (write "an error occurred: " nil)
;                    (write condition)
;                    'bummer)
;         result))
;     ; ==> bummer


;;; = (multiple-value-call function-form values-forms\*) -> result
;
; Since: 1.2
;
; `multiple-value-call` first evaluates the `function-form` to obtain function,
; and then evaluates each `values-form`. All the values of each form
; are gathered together (not just one value from each) and given as arguments
; to the function.

(multiple-value-call + 0.0 (values 1 2) 3) ; ==> 6.0

;;; = (multiple-value-bind (symbols\*) values-form bodyforms\*) -> result
;
; Since: 1.2
;
; `values-form` is evaluated, and each of the `symbols` is bound
; to the respective value returned by that form.
; If there are more `symbols` than values returned,
; `nil` is assigned to the remaining vars.
; If there are more values than symbols, the excess values are discarded.
; The symbols are bound to the values over the execution of the `bodyforms`,
; which make up an implicit progn.

(multiple-value-bind (a b) (values 'Hello\, '\ World!)
  (format nil "%s%s" a b))
;     ==> "Hello, World!"

(multiple-value-bind (a b . c) (values 1 2 3 4 5)
  (writeln a) (writeln b) (writeln c))
;     ; 1
;     ; 2
;     ; (3 4 5)
;     ; ==> (3 4 5)

(multiple-value-bind a (values 1 2 3 4 5)
  (write a))
;     ; (1 2 3 4 5)
;     ; ==> (1 2 3 4 5)


;;; = (load filespec) -> result
;
; Since: 1.1
;
; Eval the contents of the given file, return value
; is the value returned by the last form or nil
; in case of an empty file.
;
; When compiling Murmel `load` is performed at
; compile time and must appear as a toplevel form.
;
; `filespec` is not eval'd and must be a string.
; Unless filespec ends with ".lisp" the file extension
; ".lisp" will be appended.
; If filespec is an absolute path then it will be used as is.
; Otherwise the file will be searched in the same directory
; as the file that contains the `load` and after that
; in "libdir" (set with `--libdir`, "libdir" defaults to the
; directory containing jmurmel.jar).
; If `load` is entered into the REPL then the file
; will be searched in the current directory and then
; in the "libdir".

;     (load "nul") ; ==> nil, NUL is Windows specific
;     (load "lib") ; will search for lib.lisp and eval it's contents

;;; = (require module-name optional-file-path)
;
; Since: 1.1
;
; Load the given file once. Murmel maintains an internal
; set of loaded modules, and `require` will ignore
; loading files that were already loaded by comparing
; `module-name` to the set of already loaded modules.
;
; When compiling Murmel `require` is performed at
; compile time and must appear as a toplevel form.
;
; If `optional-file-path` is omitted or nil then
; `module-name` will be used as the file path.
;
; `module-name` and `optional-file-path` are not eval'd
; and must be strings.

;     (require "mlib") ; will search for the file mlib.lisp
                 ; unless the module "mlib" was already loaded

;;; = (provide module-name)
;
; Since: 1.1
;
; Set a file's modulename so that `require` won't
; load it twice.


;;; = (declaim (optimize ...
;
; `declaim` currently only supports `optimize`, others will be ignored.
; `optimize` only supports speed, others will be ignored.


;;; == Function application ===========

;;; = function call
;
; Applies the operator returned by operatorform to
; the eval'd operands
;
;     (operatorform operands*)


;;; == Backquote ======================

; Backquote "\`" starts "fill-in templates":
; backquote, comma and comma-at work similar to CL,
; except: comma-dot is not supported.

(setq a 'a-val) (setq b 'b-val) (define c 'c-val)
(define d '(d-val1 d-val2))
`((,a b) ,c ,@d)      ; ==> ((a-val b) c-val d-val1 d-val2)

(define y 'b) (define l '(a b))
(eval ``(,a ,,@l ,,y) '((a . a) (b . b) (y . y)))
;     ; ==> (a-val a-val b-val b-val)

(define x '(1 2 3))
`(normal= ,x splicing= ,@x see?)
;     ; ==> (normal= (1 2 3) splicing= 1 2 3 see?)

`(normal= ,x fakesplicing= . ,x)
;     ; ==> (normal= (1 2 3) fakesplicing= 1 2 3)


;;; == Basic Primitives ==========

;;; = (apply form argform) -> result
;
; `form` must eval to a symbol, primitive or lambda.
; `argform` must eval to a proper list. 

;(apply '+ '(1 2)) ; ==> 3.0
(apply + '(1 2)) ; ==> 3.0

;;; = (eval form) -> result<br/> (eval form env) -> result
;
; `form` will be eval'd, it must return a form.
; The optional argument `env` will be eval'd, it must return a list of `(symbol . value)`.
; If the optional argument `env` is omitted or `nil`
; then the environment for the recursive eval is "all predefined global symbols"
; else it is the concatenation of `env` and all predefined globals

(eval '(+ 1 2)) ; ==> 3.0
(eval '(+ x y) (list '(x . 2) '(y . 3))) ; ==> 5.0
(eval '(+ x y) (list (cons 'x 2) (cons 'y 3))) ; ==> 5.0


;;; == Logic, predicates

; = (eq x y) -> boolean
;
; Returns `t` if `x` and `y` are the same object, `nil` otherwise.

; = (eql x y) -> boolean
;
; Return `t` if any of the following is true
;
; - `a` and `b` are `eq`
; - `a` and `b` are numbers of the same type and have the same value
; - `a` and `b` are the same characters
;
; Examples:

(eql 2 2) ; ==> t
(eql #\a (sref "aaa" 0)) ; ==> t
(eql -0.0 0.0) ; ==> nil

; = (equal a b) -> boolean
;
; Since: 1.4
;
; Return `t` if any of the following is true:
;
; - `a` and `b` are `eql`
; - `a` and `b` are strings that have the same text value
; - `a` and `b` are bitvectors whose elements are eql
; - `a` and `b` are conses whose car and cdr are `equal` respectively


; = consp, atom, symbolp, null, listp

; = numberp, integerp, floatp
;
; - `numberp` returns `t` for all Murmel and Java number types.
; - `integerp` returns `t` for all Murmel and Java integral number types.
; - `floatp` returns `t` for Murmel and Java decimal number types.

; = characterp

; = random-state-p
;
; Since: 1.4.3

; = hash-table-p
;
; Since: 1.4

; = functionp
;
; Since: 1.3

; = vectorp, simple-vector-p
; Since: 1.3

; = stringp
;
; Return `t` for Murmel strings and all Java Objects implementing java.lang.CharSequence

; = simple-string-p, bit-vector-p, simple-bit-vector-p,
; Since: 1.3

; = (typep obj typespec) -> boolean
;
; Since: 1.4
;
; `typep` returns `t` if `obj` is of type `typespec` or of a subtype.

; = (adjustable-array-p obj) -> boolean
;
; Since: 1.3
;
; `adjustable-array-p` returns `t` if `obj` is an adjustable vector.
;
; Note that in Murmel `(adjustable-array-p 1)` returns nil
; while in Common Lisp that would signal a `type-error`. 


;;; == Conses and lists

; = (car list) -> 1st element of list

(car '(a b c)) ; ==> a

; = (cdr list) -> rest of list

(cdr '(a b c)) ; ==> (b c)

; = (cons e1 e2) -> conscell

(cons 'a 'b) ; ==> (a . b)

;;; = rplaca, rplacd
;
; Replace the value of the CAR or CDR slot of a cons cell.

(setq l '(1 2))
(rplaca l 11) ; ==> (11 2)
(rplacd l 22) ; ==> (11 . 22)

;;; = (list elems\*) -> list<br/>(list\* elems+) -> atom-or-dotted-list
;
; `list` will create a list consisting of it's arguments,
; `list*` will create a dotted list.

(list) ; ==> nil
(list 1) ; ==> (1)
(list 1 2 3) ; ==> (1 2 3)

;(list*) ; ==> error
(list* 1) ; ==> 1
(list* 1 2 3) ; ==> (1 2 . 3)

; = (append lists\*) -> list
;
; `append` nondestructively append it's arguments. All arguments except the last
; are shallow copied, all arguments except the last must be proper lists.

(append)                    ; ==> nil
(append 'a)                 ; ==> a
(append '(a b) 'c)          ; ==> (a b . c)
(append '(a b) '(c d))      ; ==> (a b c d)
(append '(a b) '(c . d))    ; ==> (a b c . d)

; = (assq key alist) -> cons or nil
;
; Since: 1.2
;
; `assq` is similar to `assoc` except `assq` compares keys using `eq`.

; = (assoc key alist) -> cons or nil
;
; `assoc` takes a key and a list of key/value tupels (lists or conses).
; The return value is the first cons whose car is equal(\*) to `key`
; or `nil` if no such cons was found. `nil`-elements in `alist` are ignored.
;
; (\*) `assoc` compares two items as if `eql` was used.
;     `assoc` considers two items as "equal" if
;
; - Both are `eq` (are the same object)
; - Both are integers or floats or characters respectively and have the same value
;
; Examples:

(assoc 'a-key '((key-1 1) (key-2 2) (a-key 3) (key-4 4)))
  ; ==> (a-key 3)
(cdr
  (assoc 'a-key '((key-1 . 1) (key-2 . 2) (a-key . 3) (key-4 . 4))))
  ; ==> 3
(assoc nil '((key-1 1) nil (nil 2) (a-key 3) (key-4 4)))
  ; ==> (nil 2)


;;; == Vectors, Sequences


; = (make-array length [element-type [adjustablep-or-capacity]]) -> vector
;
; Since: 1.3
;
; Only one-dimensional arrays of element-type `t`, `'bit` or `'character` are supported.

; = vector-length, vector-copy, vector-fill, vector-add, vector->list, list->vector
;     (vector-length v) -> length
;     (vector-copy v [adjustablep]) -> fresh-copy
;     (vector-fill v new-elem) -> vector
;     (vector-add v elem [pos]) -> position-of-added-element
;     (vector->list v) -> list
;     (list->vector lst [adjustablep]) -> vector
;
; Since: 1.3
;
; `vector-add` is similar to CL's `vector-push-extend` but with swapped parameters,
; and Murmel's `vector-add` accepts an optional parameter `pos`.

; = vector-remove
;     (vector-remove adjustable-vector pos) -> removed-element
;
; Since: 1.4.7
;
; `vector-remove` removes the element at index `pos`, moves the following elements
; and decreases the vector's size.

; = svlength, svref, svset, vector
;
; Since: 1.3
;
; Simple vectors are one-dimensional arrays
; (implementation note: or objects of class java.lang.String in case of string literals).
;
; Example usage:

(define *v* (vector 1 2 3))
(vectorp *v*) ; ==> t
(svlength *v*) ; ==> 3
(svref *v* 1) ; ==> 2

; = list->simple-vector and simple-vector->list
;
; Since: 1.3


; = string
;     (string X) -> string
;
; Since: 1.4.1
;
; `string` coerces `X` into a mutable string.
; If `X` is a mutable string, `X` is returned.
; If `X` is an immutable string, a fresh mutable simple string is returned.
; If `X` is a symbol, its name is returned.
; If `X` is a character then a one element string containing that character is returned.
; If `X` cannot be coerced into a string, an error occurs.

; = slength, sref, sset
;     (slength str) -> length
;     (sref    str n) -> nth-character
;     (sset    str n new-char) -> new-char
;
; Since: 1.3
;
; `sref` returns the n-th character of the string `str`, `n` is 0-based.
; Similar to CL `char`.
;
; `sset` sets the n-th character of `str` to `new-char`.
; Using `sset` with a string literal is an error.

; = (string= s1 s2) -> boolean

; = (string->list str) -> list-of-characters

; = (list->string list-of-characters [adjustablep]) -> string

; = (code-char integer) -> character

; = (char-code character) -> integer


; = bvlength, bvref, bvset, bv=
;     (bvref bitvector n) -> nth-bit
;     (bvset bitvector n new-bit) -> new-bit
;
; Since: 1.3
;
; `bvref` returns the n-th bit of the bitvector `bitvector`, `n` is 0-based.
; Similar to CL `bit`.
;
; `bvset` sets the n-th bit of `bitvector` to `new-bit`.

; = bit-vector->list, list->bit-vector
;     (bit-vector->list bv) -> list-of-bits
;     (list->bit-vector lst [adjustablep]) -> bitvector
;
; Since: 1.3

; = seqref, seqset
;     (seqref seq n) -> nth-element
;     (seqset seq n new-element) -> new-element
;
; Since: 1.3
;
; `seqref` is similar to CL `elt` function.
; Murmel's `seqref` and `seqset` will handle dotted lists, though.

(seqref "abc" 2) ; ==> #\c
;(seqref "abc" 3) ; ==> error
(seqref #(0 1 2 3) 3)  ; ==> 3
(seqref '(0 1 2 . 3) 3) ; ==> 3

(let ((l (list* 0 1 2)))
  (seqset l 2 22) l)
  ; ==> (0 1 . 22)


;;; == Hash-tables

; = hash-table-p, hash, make-hash-table, hashref, hashset,<br/>hash-table-count, clrhash, hash-table-remove
;
;     (hash-table-p hash-table) -> boolean
;     (hash [test [key1 value1 key2 value2...]]) -> hash-table
;     (make-hash-table [test [size]]) -> hash-table
;     (hashref hash-table key [default]) -> value, was-present-p
;     (hashset hash-table key value) -> value
;     (hashset generator value) -> value
;     (hash-table-count hash-table) -> number-of-entries
;     (clrhash hash-table) -> hash-table
;     (hash-table-remove hash-table key) -> was-present-p 
;     (hash-table-remove generator) -> was-present-p 
;
; Since: 1.4
;
; `hash-table-p, make-hash-table, hash-table-count, clrhash`
; are similar to CL's functions with the same name.
;
; `test` defaults to `eql` and is currently limited to
; `nil, t, eq, eql, compare-eql, equal, compare-equal`.
; When `t` is specified as `key` then object comparisons are done using
; Java's `Object.equals()` method.
;
; Implementation note: hashtables with `compare-eql` or `compare-equal`
; are actually implemented as trees, so operations will be O(log n).
; hashtables with `eq, eql, equal` or `t` are real hashtables, so operations will be O(n).

; = sxhash
;
;     (sxhash obj) -> hash-code
;
; Since: 1.4
;
; For two objects that are `equal` `sxhash` will return the same hash-code.

; = scan-hash-table
;
;     (scan-hash-table hash) -> key-value-generator
;
; Since: 1.4
;
; `scan-hash-table` returns a function of no arguments that will
; on subsequent invocations return `(key . value), valid?`.
;
; Murmel's (and [mlib's](mlib.md)) generators are somewhat similar to what
; SRFI 158 https://srfi.schemers.org/srfi-158/srfi-158.html
; provides.


;;; == I/O

; = read
;
;     (read eof-obj?) -> obj
;
; Read an S-expression from stdin.
;
; `read` w/o an argument will throw an error when encountering EOF.
; If an optional argument was given then EOF does not throw an error
; but the given argument is returned, e.g.:
;
;     C:\> echo (read)| java -jar lambda\target\jmurmel.jar
;     Error: read: EOF
;     error occurred in line 1:1..1:5: (read)
;
; but
;
;     C:\> echo (read 'xyxxy)| java -jar lambda\target\jmurmel.jar
;     ==> xyxxy
;
; Note that if an EOF occurs while reading an S-expression an error
; will be thrown even when `eof-obj` was used. 


; = write, writeln, lnwrite
;
;     (write   obj  [print-escape-p [dest]]) -> obj
;     (writeln [obj [print-escape-p [dest]]]) -> obj
;     (lnwrite [obj [print-escape-p [dest]]]) -> obj
;
; Write a Lisp object as an S-expression to `dest`.
;
; `write` accepts an optional boolean argument `print-escape-p`.
; `writeln` and `lnwrite` accept an optional argument `obj`
; and an optional boolean argument `print-escape-p`.
;
; `write`, `writeln` and `lnwrite` accept an optional argument `dest`
; which may be `t` or an adjustable string.
; `t` means: write to stdout, else write to `dest`.
; (Implementation note: any Java object implementing `java.lang.Appendable`
; is acceptable.)
;
; `writeln` will write the argument if given, followed by a newline.  
; `lnwrite` will write a newline followed by the argument if given,
; followed by a ' ', i.e. writeln is C-style, lnwrite is Lisp-style.

(writeln "Hello, ")
(writeln)
(writeln "World!")

; `write`, `writeln` and `lnwrite` will escape atoms by default,
; the optioal parameter `print-escape-p` can be used to turn off escaping:

(writeln "Hello, World!" nil)


; = (write-to-string obj print-escape-p?) -> result-string
;
; Since: 1.4
;
; Convert `obj` to it's string representation.


; = (read-from-string str [eof-obj [start [end]]]) -> object, position
;
; Since: 1.4
;
; Similar to CL's `read-from-string` which has more parameters.
; If `eof-obj` is not given or `nil` then end-of-file during reading
; will be signalled as an `end-of-file` condition.

(read-from-string "123 456" nil 4)     ; ==> 456, 7
(read-from-string "123 456" 'eof 7)    ; ==> eof, 7
(read-from-string "123 456   " 'eof 7) ; ==> eof, 10
(read-from-string "123 456" nil 1 4)   ; ==> 23, 4
(read-from-string "          " 'eof 5) ; ==> eof, 10


; = (read-textfile-lines filename [charset]) -> result-string-vector
;
; Since: 1.4
;
; Read the file with the given filename (or stdin if `filename` is `t`) and return it's contents
; as a `simple-vector` containing one `simple-string` for each line.
;
; If `charset` is `nil` then `UTF-8` will be used.


; = (read-textfile filename [charset [translate-lineend-p]]) -> result-string
;
; Since: 1.4
;
; Read the file with the given filename (or stdin if `filename` is `t`)
; and return it's contents as a mutable `string`.
;
; If `charset` is `nil` then `UTF-8` will be used.
;
; If `translate-lineend-p` is omitted or non-nil then (possibly OS-dependent)
; lineend character sequences will be normalized to `#\Newline`.
;
; `charset` defaults to UTF-8.


; = (write-textfile-lines filename string-sequence  [appendp [charset [translate-lineend-p]]]) -> nil
;
; Since: 1.4
;
; Write all elements (which must be of type `string`)
; of `string-sequence` to the file `filename` (or stdout if `filename` is `t`).
; Each element (line) will be terminated with the OS-default line-end character(-sequence).
; (Note: with the JVM this can be set using -Dline.separator.)
;
; If `charset` is `nil` then `UTF-8` will be used.
;
; If `translate-lineend-p` is omitted or non-nil then each #\Newline character
; will be written as the OS-dependent line-end character(-sequence).


; = (write-textfile filename string  [appendp [charset [translate-lineend-p]]]) -> nil
;
; Since: 1.4
;
; Write `string` to the file `filename` (or stdout if `filename` is `t`).
;
; If `charset` is `nil` then `UTF-8` will be used.
;
; If `translate-lineend-p` is omitted or non-nil then each #\Newline character
; will be written as the OS-dependent line-end character(-sequence).


; = (format dest formatstr args*), (format-locale dest locale formatstr args*)
;
; The first argument `dest` can be `t`, `nil` or an adjustable string.
;
; `format t` writes a formatted string to stdout and returns `nil`.
; `format`'s parameters work as with `java.lang.String.format()`
; which is similar to C's `printf()`.

(format t
  "a string: %s, a number: %g, a newline:%n" "The String" 3.14)

; `format-locale` works similar to format except it has an additional
; second string parameter that should be a locale, `nil` means use Java's
; default locale.

(format-locale t "de-DE"
  "a string: %s, a number: %g, a newline:%n" "The String" 3.14)

; `format nil` and `format-locale nil` work similar
; to `format t` and `format-locale t` except they don't write to stdout
; but return the string.

(format-locale nil "de-DE"
  "a string: %s, a number: %g, a newline:%n" "The String" 3.14)


;;; = Misc

;;; = (values object\*) -> multiple-values
;
; Since: 1.2
;
; `values` returns the objects as multiple values.

; = (gensym [optional-name]) -> uninterned symbol
;
; Return a new uninterned symbol.
(gensym)

; = (macroexpand-1 quoted-form) -> expanded-form, boolean
;
; `macroexpand-1` is a simplified version of CL's `macroexpand-1`.
; It is only fully supported in interpreted code,
; in compiled code `macroexpand-1` does quoted forms only.
; If the operator of the list `quoted-form` is a macroname then
; the macrocall will be expanded, and the secondary return value
; will be `t`, e.g.:

(defmacro add2 (a) `(+ ,a 2))  ; ==> add2
(macroexpand-1 '(add2 3))      ; --> (+ 3 2)
                               ; --> t

; = (error datum . arguments) -> |
;
; Since 1.4
;
; Similar to CL's `error`.
; `datum` can also be a condition,
; e.g. to re-raise a condition that is not handled.

(try (error 'simple-error "an error occurred") 'err)
  ; -> err
  ; -> simple-error - an error occurred

(writeln (try (multiple-value-bind (result condition)
                                   (try (error 'simple-error "an error occurred") 'err)
                (if (eq result 'err)
                    (if (typep condition 'arithmetic-error)
                        (writeln "an arithmetic error occurred")
                        (progn (writeln "another error occurred, rethrowing")
                               (error condition)))
                    (writeln "no error")))

              'outer-err))  ; ==> outer-err


; = lisp-implementation-type, lisp-implementation-version
;
; Since: 1.4.5
;
; Similar to CL's functions of the same name.


;;; == Time

; = (get-internal-real-time) -> number
;
; Walltime in internal time units, relative to an arbitrary time base

(get-internal-real-time)

; = (get-internal-run-time) -> number
;
; User cpu time in internal time units

(get-internal-run-time)

; = (sleep desired-duration) -> nil
;
; Pause execution for approx. x seconds.
; This example code will pause execution for approx. 1 second.

(sleep 1)

; = (get-universal-time) -> seconds since 1.1.1900 00:00:00 UTC
;
; This example code will return approx. years since 1.1.1900

(/ (get-universal-time) 60 60 24 365)

; = (get-decoded-time) -> second, minute, hour, date, month, year, day, daylight-p, zone
;
; NOTE: In Common Lisp zone is given as a a rational multiple of 1/3600 of hours
;       offset from Greenwich Mean Time.
;       In Murmel zone is given as a double, e.g. Vienna in winter is -1.0.
;       The result type of Murmel's (get-decoded-time) is a list
;       while CL's returns an ordered sequence.

(get-decoded-time)


;;; == Predefined Numeric Primitives ==

;;; Murmel's two numeric datatypes are implemented as `long` (54 bit signed integer)
;;; and `double` (64 bit floating point).
;;; Other Java datatypes (which may occur when using Java FFI) will be automatically converted
;;; (with null-, lost-precision- and over/underflow checks) as appropriate.
;;;
;;; Murmel does most maths in double precision:
;;;
;;; - Except with `1+, 1-, ceiling, floor, round, truncate and signum`,
;;;   arguments to numeric functions will be converted to `double`,
;;;   and the result will be `double`.  
;;;   Integer over/underflow during argument conversion will be signalled as an error.
;;;   Results for large numbers (i.e. over/ underflow) will go towards +/- Infinity.
;;; - `1+, 1-`: Byte, Short, Integer and Long arguments will be converted to long,
;;;   in that case the result type is long. Over/ underflow of the result will be signalled as an error.
;;;   Other argument types will be handled as above.
;;; - `ceiling, floor, round, truncate`: result type is long, over/ underflow will be signalled as an error.
;;; - `signum`: result is a "signed prototype" - either `long -1/0/1` or `double -1.0/-0.0/0.0/1.0`.

; = +, -, \*, /, mod, rem, sqrt, log, log10, exp, expt
;
; The math operators accept numbers only.
; All numeric operators return a double.
; eg. `(+ number number) -> double`.

(+ 1 1) ; ==> 2.0

; = 1+, 1-
;
; Increment and decrement return the same type as the argument.

(1+ 1)   ; ==> 2
(1+ 1.0) ; ==> 2.0

; = round, truncate, floor, ceiling
;
; These functions take one or two arguments and return an integer value or an exception
; if the value cannot be represented by a long
; (NaN, Infinite, integer overflow or underflow),
; eg. `(floor number) -> long`

(floor 1.1) ; ==> 1

; = fround, ftruncate, ffloor, fceiling
;
; These functions take one or two arguments and return an integer value as a double,
; eg. `(ffloor number) -> double`

(ffloor 1.1) ; ==> 1.0

; = (signum number) -> signed-prototype
;
; `signum` determines a numerical value that indicates whether
; number is negative, zero, or positive. 

(signum 0)    ; => 0
(signum -0)   ; => 0
(signum 3)    ; => 1
(signum -3)   ; => -1

(signum 0.0)  ; => 0.0
(signum -0.0) ; => -0.0
(signum 3.0)  ; => 1.0
(signum -3.0) ; => -1.0

; = = < > <= >= /=
;
; The numeric comparison operators take one or more number arguments.

(= 1 1.0)         ; ==> t
(< 1 2 3.0 4 5.0) ; ==> t
(< 1 2 3 3 4 5)   ; ==> nil

; = (random limit random-state?) -> random-number
;
; Since: 1.4.3
;
; Similar to CL's `random`.

; = (make-random-state state?) -> new-state
;
; Since: 1.4.3
;
; Similar to CL's `make-random-state` with the following differences:
; - If `state` is a number then it will be truncated to an integer
;   and used as a seed for the newly created random state.
; - Murmel's `random-state` objects will print unreadably.


;;; == Predefined Graphics Primitives =

;;; Murmel features primitives for graphics output to a frame.
;;;
;;; A frame is a toplevel GUI window with a title. One can write text on a frame,
;;; and/ or draw lines with Turtle graphics or moveto/lineto functions.
;;; Also one can attach a bitmap to a frame and use pixel-graphics primitives.
;;;
;;; 0/0 is towards left bottom, any drawing will be resized/ shifted so that
;;; it fills the frame.
;;;
;;; A frame has state: open/closed, current x/y position, current linecolor,
;;; current turtle angle and background color.
;;;
;;; One can use several frames but only one is the "current-frame". All functions
;;; (except `make-frame`) have an optional last parameter `frame` that can be used
;;; to select which frame to operate on (if omitted or `nil` then the current frame is used).
;;;
;;; Hint: if graphics primitives are slow then maybe switching to OpenGL
;;; will speed things up:
;;;
;;;     C:\> java -Dsun.java2d.opengl=true -jar jmurmel.jar
;;;
;;; Colors are 0..15 corresponding to
;;;
;;;       0 ; white
;;;       1 ; black
;;;       2 ; red
;;;       3 ; green
;;;       4 ; blue
;;;       5 ; pink
;;;       6 ; orange
;;;       7 ; yellow
;;;       8 ; magenta
;;;       9 ; cyan
;;;      10 ; darkGray
;;;      11 ; gray
;;;      12 ; lightGray
;;;      13 ; darkred
;;;      14 ; darkgreen
;;;      15 ; darkblue

; = (make-frame window-title optwidthpixels optheightpixels optpaddingpixels) -> frame
;
; Creates a new frame, sets current frame.
; If width and height are omitted or nil then half of the physical screen
; width/ height will be used.
; If padding is omitted or nil then 40 will be used.
; The newly created frame will not yet be visible (see open-frame below).

;     (let ((window-title "test")
;           (optwidthpixels 100)
;           (optheightpixels 100)
;           (optpaddingpixels 10))
;       (make-frame window-title
;         optwidthpixels optheightpixels optpaddingpixels))
;       ; ==> frame

; = (current-frame) -> frame
;
; Returns current frame.

; = (current-frame optional-frame) -> frame
;
; Set new current frame, returns previous current frame.

; = More frame-functions
;
; `open-frame` ... make frame visible  
; `close-frame` ... hide frame  
; `reset-frame` ... reset pen to "down", turtle position and angle, color and bgcolor    
; `clear-frame` ... reset frame and discard frame contents  
; `repaint-frame` ... force full repaint  
; `flush-frame` ... paint operations won't take immediate effect, flush-frame makes them visible  
; `pen-up` ... subsequent line operations will only move the position  
; `pen-down` ... subsequent line operations will have visible effect  
; `push-pos` ... save current position and angle  
; `pop-pos` ... restore previous position and angle
;
; The above functions all take one optional frame parameter. If omitted or `nil`
; then the current frame will be used.

; = (color color optional-frame) -> frame
;
; Set color for following lines, color must be >= 0 and <= 12

;     (color 1) ; ==> frame

; = (bgcolor color optional-frame) -> frame
;
; Set background color for frame, color must be >= 0 and <= 12

;     (bgcolor 0) ; ==> frame

; = (text str optional-frame) -> frame
;
; Writes str at current position, does not change position.

; = (left  deg optional-frame) -> frame</br>(right deg optional-frame) -> frame
;
; Increase/ decrease current angle by `deg` degrees, does not change position.

; = (forward len optional-frame) -> frame
;
; If pen is down then this function paints a line of length `len` from current
; position in current direction, changes position.
; If pen is up then only the position is changed.

; = move-to, line-to, move-rel, line-rel
;
; These functions take two arguments denoting the new position
; and an optional frame argument.

;     (define new-x 1)
;     (define new-y 2)
;     (define optional-frame nil)
;     (line-rel new-x new-y optional-frame) ; ==> frame

; = (make-bitmap w h optional-frame) -> frame
;
; Associates a bitmap of the given width and height
; with the current or given frame. The bitmap will be scaled
; to fill the frame.
;
; = (discard-bitmap optional-frame)
;
; Remove the bitmap of the given or current frame,
; and release the resources associated with the bitmap.
;
; = (rgb-to-pixel r g b) -> 24bit color value acceptable to set-pixel
;
; `r`, `g` and `b` are 0..255
;
; = (hsb-to-pixel h s b) ; -> 24bit color value acceptable to set-pixel
;
; `h`, `s` and `b` are 0..1.0
;
; = (set-pixel x y color-as-24-bit optional-frame) -> frame
;
; Set pixel at the given xy-position to the given color.

;;; --- End of Murmel reference ---


;;; == Extensions =====================

; JMurmel adds some extra features to Murmel which are listed below.

; = lambda dynamic
;
; For experimentation purposes the interpreter also supports
; lambdas that are not lexical closures.
;
; When the optional keyword `dynamic` is given then
; no environment is captured, and lambdas - when applied -
; get the dynamic environment.
;
;     (lambda dynamic (params*) forms*) -> anonymous function with
;                                          dynamic environment

; = Custom primitives
;
; In embedded use primitives may be added, also Java methods
; created by the primitive `jmethod` (see below) act as builtins.
; As far as the language is concerned, all primitives are variadic functions.
; The primitives themselves may have parameter checks, tough.
; In case they are called with the wrong type(s) or number of parameters
; the primitives may throw an error.

; = Language subsets
;
; JMurmel supports commandline parameters that can be used to
; disable many of Murmel's forms, predefined variables, ... .
; These commandline parameters can be used to experiment
; with an even more reduced Lisp.
;
; See `jmurmel --help-features`.


;;; == Additional JMurmel special forms and primitives ==========

; = (trace function-name\*) -> trace-result<br/> (untrace function-name\*) -> untrace-result
;
; Arguments to trace/ untrace are eval'd.
; In interpreted code these work similar to CL's trace/ untrace macros.
; Only interpreted code will be traced (user defined functions as well as
; interpreter primities, primitives are only traced if speed=0).

(trace 'write '+)  
(write (+ 1 2))  
(untrace)


;;; == Java FFI

; = (jmethod classname methodname paramclasses\*) -> primitive
;
; The primitive `jmethod` will return a newly created primitive
; that is implemented by the method `methodname` of the Java class
; `classname` that has the formal parameters `paramclasses*`.
; Parameters to `jmethod` must be strings.

(jmethod "java.lang.System" "currentTimeMillis")

; When invoking primitives created by `jmethod` the first argument must be
; a Java object of the primitive's method's class. This is not the case
; for static methods.
;
; Invoke a static method:

(define ctm (jmethod "java.lang.System" "currentTimeMillis"))  
(ctm) ; ==> 1704017140837 (actual result will vary)

; Invoke an instance method on an object:

(define make-hash (jmethod "java.util.HashMap" "new"))
(define put-hash (jmethod "java.util.Map" "put"
                          "java.lang.Object" "java.lang.Object"))
(define my-hash (make-hash))
(put-hash my-hash "key-1" "value-1")
(write my-hash)  ; ==> #H(t "key-1" "value-1")


; = (jproxy interfacename [javamethodname symbol-or-lambda]\*) -> Java-object
;
; Since: 1.2
;
; The primitive `jproxy` takes a Java interface name and zero or more
; methodname/ murmelcode tupels, and returns a Java object that implements
; `interfacename`.


;;; == Known issues ===================
;
; Murmel language:
;
; - eval-when
; - multithreading
;
; Compiler issues:
;
; - `define`/ `defun`/ `defmacro` only work as top level forms
;   or within `progn, let, let*, letrec, labels` or `multiple-value-bind` forms,
;   other use as non-toplevel form will throw a "not-yet-implemented" compiler error.
; - `define`-ing an already `define`-d symbol is not supported
; - `macroexpand-1` is limited to quoted forms
; - macro expansion is only done at compiletime, e.g. `(defmacro m() 1) (eval '(m))`
;   won't work
; - reassigning predefined primitives with `setq` is not supported, e.g.
;   `(setq trunc (lambda (p) (1+ p)))` is an error (and wouldn't make much sense)


;;; == Copyright ======================
;;;
;;; Murmel and JMurmel are Copyright (C) 2020-2024 Robert Mayer.
;;;
;;; This work is licensed under the terms of the MIT license.
;;; For a copy, see https://opensource.org/licenses/MIT.