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[HOWTO] How Do I Do X with Red
This is intended to be a collaborative list of how to perform common programming tasks with Red.
Help Command
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Display help about the help command
helpThe help command is a very powerful tool. Typinghelpat the repl will display information about all of the things help can do for you. Some really important callouts:-
help printwill display information about theprintfunction. -
help "print"will display all functions which have the string "print" in them, or their descriptions. Notice the"! -
?? printwill display the source code for the print function.
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>> help
Use HELP or ? to view built-in docs for functions, values
for contexts, or all values of a given datatype:
help append
? system
? function!
To search for values by name, use a word:
? pri
? to-
To also search in function specs, use a string:
? "pri"
? "issue!"
Other useful functions:
?? - Display a word and the value it references
probe - Print a molded value
source - Show a function's source code
what - Show a list of known functions or words
about - Display version number and build date
quit - Leave the Red consolePrinting stuff
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Print a value followed by a newline -
print
>> print "Hello Red"
Hello Red>> print ["2 x 2 =" 2 * 2]
2 x 2 = 4-
Print a word and the value it refers to -
??
>> n: 42
== 42
>> ?? n
n: 42-
Print something and return its value -
probe
>> probe n
42
== 42Reading stuff
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Get console user input -
input
>> i: input ; set i to the value returned from the input function
hi
== "hi">> i
== "hi"-
Get console user input with a prompt -
ask
>> i: ask "Who are you? "
Who are you? ME
== "ME"-
Read from a file, or url
>> read %day1.txt
== {1810^/1729^/1857^/1777^/1927^/1936^/1797^/1719^/1703^/1758^/1768^/2008^/1963^/1925^/1919^/...>> read %Downloads/
== [%jdk-15.0.1_linux-x64_bin.deb %20201104_003631.jpg %20201107_105256.jpg %Ge...>> read https://www.red-lang.org/p/getting-started.html
== {<!DOCTYPE html>^/<html class='v2' dir='ltr' xmlns='http://www.w3.org/1999/xh...-
Read a specific line from a file -
read/lines,pick
>> pick read/lines %day1.txt 42
== "1912"help read in the Red console.
> help read
USAGE:
READ source
DESCRIPTION:
Reads from a file, URL, or other port.
READ is an action! value.
ARGUMENTS:
source [file! url!]
REFINEMENTS:
/part => Partial read a given number of units (source relative).
length [number!]
/seek => Read from a specific position (source relative).
index [number!]
/binary => Preserves contents exactly.
/lines => Convert to block of strings.
/info =>
/as => Read with the specified encoding, default is 'UTF-8.
encoding [word!] Writing stuff
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Write to a File or URL
>> write %Hi.adoc "### Hello">> my-asciidoc: {
{ '''
{ * Write to a file
{
{ ```red
{ write %Hi.adoc "### Hello"
{ ```
{ }
== {^/'''^/* Write to a file^/^/```red^/write %Hi.adoc "### Hello"^/```^/}>> write/append %Hi.adoc my-asciidochelp write in the Red console.
>> help write
USAGE:
WRITE destination data
DESCRIPTION:
Writes to a file, URL, or other port.
WRITE is an action! value.
ARGUMENTS:
destination [file! url! port!]
data [any-type!]
REFINEMENTS:
/binary => Preserves contents exactly.
/lines => Write each value in a block as a separate line.
/info =>
/append => Write data at end of file.
/part => Partial write a given number of units.
length [number!]
/seek => Write at a specific position.
index [number!]
/allow => Specifies protection attributes.
access [block!]
/as => Write with the specified encoding, default is 'UTF-8.
encoding [word!] Interogating stuff
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Get the current directory
>> what-dir
== %/home/gt/-
List the contents of the current directory
> list-dir %Downloads/
jdk-15.0.1_linu... 20201104_003631... 20201107_105256...
Get_Programming... >> list-dir what-dir
Pictures/ .themes/ tmp/
.profile red .lazarus/
.gtkrc-xfce email HowDo.adoc
pm-tup.hs .sudo_as_admin_... Documents/ help list-dir in the Red console.
>> help list-dir
USAGE:
LIST-DIR dir
DESCRIPTION:
Displays a list of files and directories from given folder or current one.
LIST-DIR is a function! value.
ARGUMENTS:
dir [any-type!] "Folder to list."
REFINEMENTS:
/col => Forces the display in a given number of columns.
n [integer!] "Number of columns."-
Get file size -
size?From: https://rosettacode.org/wiki/File_size#Red
>> size? %input.txt
== 39244
>> size? %/c/input.txt
== 39244-
Check if a file exists -
exists?
> exists? %day1.txt
== true
>> exists? %some-file.txt
== false-
Create a Window (bare minimum)
view []-
Create a Window with a title and size constraints
view [title "HAL 9000" size 800x600]Start with VID for easy graphics: https://github.com/red/docs/blob/master/en/vid.adoc
Move to the View for more power: https://github.com/red/docs/blob/master/en/view.adoc
Have a look at Draw if you’re into drawing things: https://github.com/red/docs/blob/master/en/draw.adoc
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A basic editor
view/options/flags [
title "Basic Editor"
editor: area 800x600 on-change [face/parent/actors/saved?: no]
][
menu: ["File" ["Open" open "Save" save "Quit" quit]]
actors: object [
on-menu: func [face event][
switch event/picked [
open [open-file face]
save [save-file]
quit [check-saving]
]
]
on-close: does [check-saving]
on-resizing: func [face event][
editor/size: face/size - 20
]
on-resize: func [face event][on-resizing face none]
check-saving: does [unless saved? [confirm] unview] ; or `quit` but this kills console too
saved?: yes
file: none
open-file: func [face][
if file: request-file [
editor/text: read file
face/text: form file
]
]
save-file: does [
file: any [file "New"]
if file: request-file/save/file file [
write file editor/text
saved?: yes
]
]
confirm: does [
view [
title "Confirm"
text "Save file?" return
button "Yes" [save-file unview]
button "No" [unview]
]
]
]
] 'resize-
Split a string -
split>> split "abc,def,gh" #"," == ["abc" "def" "gh"] >> split "Hello Red" space == ["Hello" "Red"]
help split in the Red console
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Replace values in a string -
replace
>> s: "Red is fun?"
== "Red is fun?"
>> replace s "?" "!"
== "Red is fun!"
>> replace/all "Mississippi" "i" "*"
== "M*ss*ss*pp*"help replace in the Red console.
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Remove whitespace or other pesky characters -
trim
>> trim/all "one two three"
== "onetwothree"
>> trim/with "one two three" "t"
== "one two hree"help trim in the Red console.
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Convert a string (ex: file name) so it can be read by a browser -
enhex
>> to file! enhex "0! @#ok.png"
== %"0%21%20%20%40%23ok.png"`help enhex ` in the Red console.
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Parse a string
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Install Red: https://www.red-lang.org/p/download.html
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Use the REPL, play with Red, try red
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Write a function
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Include type specs for function args
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Define an array/map/struct
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Specify a datatype for a variable
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Objects: https://www.red-lang.org/search?q=Object
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Create an OOP class
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Inherit from an object
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Implement an OO interface
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Create private/protected members in an object
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Find out what methods an object or datatype supports
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Find out what datatypes are available in Red, and how to use them
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Enforce immutability
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Pass values by reference or by value to functions
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Create a lambda/anonymous function
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Get the name of the function being called
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Make HTTP requests (read URLs)
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Access an API that uses JSON
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Use command line arguments to Red scripts
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Call/launch other programs, including redirecting I/O
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Call C functions in DLLs
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Convert Red/System values to the Red ones
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Compile and cross compile
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Import a library, load a module, use a package manager
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Set the icon for an EXE
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Use HTML in a Red GUI
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Write Javascript code in Red
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Include a web-browser component in a Red GUI
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Do machine learning
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Use regular expressions
Both Red and Red/System are published under the BSD license. The runtime is published under the BSL license.