hs.fnutils.md

docs » hs.fnutils

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Functional programming utility functions

API Overview

• Functions - API calls offered directly by the extension
• concat
• contains
• copy
• each
• every
• filter
• find
• ieach
• ifilter
• imap
• indexOf
• map
• mapCat
• reduce
• some
• split
• Constructors - API calls which return an object, typically one that offers API methods
• cycle
• partial
• sequence
• sortByKeys
• sortByKeyValues

API Documentation

Functions

concat

Signature	hs.fnutils.concat(table1, table2)
Type	Function
Description	Join two tables together
Parameters	table1 - A table containing some sort of data table2 - A table containing some sort of data
Returns	table1, with all of table2's elements added to the end of it
Notes	table2 cannot be a sparse table, see http://www.luafaq.org/gotchas.html#T6.4

contains

Signature	hs.fnutils.contains(table, element) -> bool
Type	Function
Description	Determine if a table contains a given object
Parameters	table - A table containing some sort of data element - An object to search the table for
Returns	A boolean, true if the element could be found in the table, otherwise false

copy

Signature	hs.fnutils.copy(table) -> table
Type	Function
Description	Copy a table using pairs()
Parameters	table - A table containing some sort of data
Returns	A new table containing the same data as the input table

each

Signature	hs.fnutils.each(table, fn)
Type	Function
Description	Execute a function across a table (in arbitrary order), and discard the results
Parameters	table - A table; it can have both a list (or array) part and a hash (or dict) part fn - A function that accepts a single parameter (a table element)
Returns	None

every

Signature	hs.fnutils.every(table, fn) -> bool
Type	Function
Description	Returns true if the application of fn on every entry in table is true.
Parameters	table - A table containing some sort of data fn - A function that accepts a single parameter and returns a "true" value (any value except the boolean false or nil) if the parameter was accepted, or a "false" value (the boolean false or nil) if the parameter was rejected.
Returns	True if the application of fn on every element of the table is true False if the function returns false for any element of the table. Note that testing stops when the first false return is detected.

filter

Signature	hs.fnutils.filter(table, fn) -> table
Type	Function
Description	Filter a table by running a predicate function on its elements (in arbitrary order)
Parameters	table - A table; it can have both a list (or array) part and a hash (or dict) part fn - A function that accepts a single parameter (a table element) and returns a boolean value: true if the parameter should be kept, false if it should be discarded
Returns	A table containing the elements of the table for which fn(element) returns true
Notes	If table is a pure array table (list-like) without "holes", use hs.fnutils.ifilter() if you need guaranteed in-order processing and for better performance.

find

Signature	hs.fnutils.find(table, fn) -> element
Type	Function
Description	Execute a function across a table and return the first element where that function returns true
Parameters	table - A table containing some sort of data fn - A function that takes one parameter and returns a boolean value
Returns	The element of the supplied table that first caused fn to return true

ieach

Signature	hs.fnutils.ieach(list, fn)
Type	Function
Description	Execute a function across a list-like table in order, and discard the results
Parameters	list - A list-like table, i.e. one whose keys are sequential integers starting from 1 fn - A function that accepts a single parameter (a table element)
Returns	None

ifilter

Signature	hs.fnutils.ifilter(list, fn) -> list
Type	Function
Description	Filter a list-like table by running a predicate function on its elements in order
Parameters	list - A list-like table, i.e. one whose keys are sequential integers starting from 1 fn - A function that accepts a single parameter (a table element) and returns a boolean value: true if the parameter should be kept, false if it should be discarded
Returns	A list-like table containing the elements of the table for which fn(element) returns true
Notes	If list has "holes", all elements after the first hole will be lost, as the table is iterated over with ipairs; use hs.fnutils.map() if your table has holes

imap

Signature	hs.fnutils.imap(list, fn) -> list
Type	Function
Description	Execute a function across a list-like table in order, and collect the results
Parameters	list - A list-like table, i.e. one whose keys are sequential integers starting from 1 fn - A function that accepts a single parameter (a table element). The values returned from this function will be collected into the result list; when nil is returned the relevant element is discarded - the result list won't have any "holes".
Returns	A list-like table containing the results of calling the function on every element in the table
Notes	If list has "holes", all elements after the first hole will be lost, as the table is iterated over with ipairs; use hs.fnutils.map() if your table has holes

indexOf

Signature	hs.fnutils.indexOf(table, element) -> number or nil
Type	Function
Description	Determine the location in a table of a given object
Parameters	table - A table containing some sort of data element - An object to search the table for
Returns	A number containing the index of the element in the table, or nil if it could not be found

map

Signature	hs.fnutils.map(table, fn) -> table
Type	Function
Description	Execute a function across a table (in arbitrary order) and collect the results
Parameters	table - A table; it can have both a list (or array) part and a hash (or dict) part fn - A function that accepts a single parameter (a table element). For the hash part, the values returned from this function (if non-nil) will be assigned to the same key in the result list. For the array part, this function behaves like hs.fnutils.imap() (i.e. nil results are discarded); however all keys, including integer keys after a "hole" in table, will be iterated over.
Returns	A table containing the results of calling the function on every element in the table
Notes	If table is a pure array table (list-like) without "holes", use hs.fnutils.imap() if you need guaranteed in-order processing and for better performance.

mapCat

Signature	hs.fnutils.mapCat(table, fn) -> table
Type	Function
Description	Execute, across a table, a function that outputs tables, and concatenate all of those tables together
Parameters	table - A table containing some sort of data fn - A function that takes a single parameter and returns a table
Returns	A table containing the concatenated results of calling fn(element) for every element in the supplied table

reduce

Signature	hs.fnutils.reduce(table, fn) -> table
Type	Function
Description	Reduce a table to a single element, using a function
Parameters	table - A table containing some sort of data fn - A function that takes two parameters, which will be elements of the supplied table. It should choose one of these elements and return it
Returns	The element of the supplied table that was chosen by the iterative reducer function
Notes	table cannot be a sparse table, see http://www.luafaq.org/gotchas.html#T6.4 The first iteration of the reducer will call fn with the first and second elements of the table. The second iteration will call fn with the result of the first iteration, and the third element. This repeats until there is only one element left

some

Signature	hs.fnutils.some(table, fn) -> bool
Type	Function
Description	Returns true if the application of fn on entries in table are true for at least one of the members.
Parameters	table - A table containing some sort of data fn - A function that accepts a single parameter and returns a "true" value (any value except the boolean false or nil) if the parameter was accepted, or a "false" value (the boolean false or nil) if the parameter was rejected.
Returns	True if the application of fn on any element of the table is true. Note that testing stops when the first true return is detected. False if the function returns false for all elements of the table.

split

Signature	hs.fnutils.split(sString, sSeparator [, nMax] [, bPlain]) -> { array }
Type	Function
Description	Convert string to an array of strings, breaking at the specified separator.
Parameters	sString -- the string to split into substrings sSeparator -- the separator. If bPlain is false or not provided, this is treated as a Lua pattern. nMax -- optional parameter specifying the maximum number (or all if nMax is nil) of substrings to split from sString. bPlain -- optional boolean parameter, defaulting to false, specifying if sSeparator should be treated as plain text (true) or a Lua pattern (false)
Returns	An array of substrings. The last element of the array will be the remaining portion of sString that remains after nMax (or all, if nMax is not provided or is nil) substrings have been identified.
Notes	Similar to "split" in Perl or "string.split" in Python. Optional parameters nMax and bPlain are identified by their type -- if parameter 3 or 4 is a number or nil, it will be considered a value for nMax; if parameter 3 or 4 is a boolean value, it will be considered a value for bPlain. Lua patterns are more flexible for pattern matching, but can also be slower if the split point is simple. See §6.4.1 of the Lua_Reference_Manual at http://www.lua.org/manual/5.3/manual.html#6.4.1 for more information on Lua patterns.

Constructors

cycle

Signature	hs.fnutils.cycle(table) -> fn()
Type	Constructor
Description	Creates a function that repeatedly iterates a table
Parameters	table - A table containing some sort of data
Returns	A function that, when called repeatedly, will return all of the elements of the supplied table, repeating indefinitely
Notes	table cannot be a sparse table, see http://www.luafaq.org/gotchas.html#T6.4 An example usage: lua f = cycle({4, 5, 6}) {f(), f(), f(), f(), f(), f(), f()} == {4, 5, 6, 4, 5, 6, 4}

partial

Signature	hs.fnutils.partial(fn, ...) -> fn'
Type	Constructor
Description	Returns a new function which takes the provided arguments and pre-applies them as the initial arguments to the provided function. When the new function is later invoked with additional arguments, they are appended to the end of the initial list given and the complete list of arguments is finally passed into the provided function and its result returned.
Parameters	fn - The function which will act on all of the arguments provided now and when the result is invoked later. ... - The initial arguments to pre-apply to the resulting new function.
Returns	A function
Notes	This is best understood with an example which you can test in the Hammerspoon console:

sequence

Signature	hs.fnutils.sequence(...) -> fn
Type	Constructor
Description	Creates a function that will collect the result of a series of functions into a table
Parameters	... - A number of functions, passed as different arguments. They should accept zero parameters, and return something
Returns	A function that, when called, will call all of the functions passed to this constructor. The output of these functions will be collected together and returned.

sortByKeys

Signature	hs.fnutils.sortByKeys(table[ , function]) -> function
Type	Constructor
Description	Iterator for retrieving elements from a table of key-value pairs in the order of the keys.
Parameters	table - the table of key-value pairs to be iterated through fn - an optional function which will be passed to table.sort to determine how the keys are sorted. If it is not present, then keys will be sorted numerically/alphabetically.
Returns	function to be used as an iterator
Notes	Similar to Perl's sort(keys %hash) Iterators are used in looping constructs like for: for i,v in hs.fnutils.sortByKeys(t[, f]) do ... end A sort function should accept two arguments and return true if the first argument should appear before the second, or false otherwise. e.g. function(m,n) return not (m < n) end would result in reverse alphabetic order. See Programming_In_Lua,_3rd_ed, page 52 for a more complete discussion. The default sort is to compare keys directly, if they are of the same type, or as their tostring() versions, if the key types differ: function(m,n) if type(m) ~= type(n) then return tostring(m) < tostring(n) else return m < n end

sortByKeyValues

Signature	hs.fnutils.sortByKeyValues(table[ , function]) -> function
Type	Constructor
Description	Iterator for retrieving elements from a table of key-value pairs in the order of the values.
Parameters	table - the table of key-value pairs to be iterated through fn - an optional function which will be passed to table.sort to determine how the values are sorted. If it is not present, then values will be sorted numerically/alphabetically.
Returns	function to be used as an iterator
Notes	Similar to Perl's sort { $hash{$a} <=> $hash{$b} } keys %hash Iterators are used in looping constructs like for: for i,v in hs.fnutils.sortByKeyValues(t[, f]) do ... end A sort function should accept two arguments and return true if the first argument should appear before the second, or false otherwise. e.g. function(m,n) return not (m < n) end would result in reverse alphabetic order. See Programming_In_Lua,_3rd_ed, page 52 for a more complete discussion. The default sort is to compare values directly, if they are of the same type, or as their tostring() versions, if the value types differ: function(m,n) if type(m) ~= type(n) then return tostring(m) < tostring(n) else return m < n end