View source for Comparison of programming languages (functional programming)

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This page provides the comparison tables of [[functional programming]] instructions between programming languages. Comparison of basic instructions of [[imperative paradigm]] is provided by [[Comparison of programming languages (basic instructions)|the comparison of basic instructions]].

== List operations ==

=== Function applications and lists ===
For brevity, these words will have the specified meanings in the following tables (unless noted to be part of language syntax):

;{{mono|funcN}}: A function. May be unary or n-ary (or always unary for languages without n-ary functions).
:;{{mono|func1}}, {{mono|func2}}, etc.: functions of specific arity. {{mono|func}} (with no number) is the same as {{mono|func1}}, also known as a ''projection'' in many languages.
;{{mono|pred}}: Unary function returning a Boolean value. ([[ML (programming language)|ML]] type: {{mono|'a -> bool}}) (C-like type: {{code|bool pred<T>(T t)|cpp}}).
;{{mono|{{var|list}}}}: The list being operated on.
;{{mono|{{var|args}}}}: Comma-separated list of one or more argument names, in the form of {{mono|{{var|arg1, arg2, ..., argn}}}}.
;{{mono|pattern}}: A pattern, in languages with [[pattern matching]].
;{{mono|val}}: Any relevant value, depending on context.

{| class="wikitable"
!
! identity lambda
! lambda
![[Map (higher-order function)|map]]
![[apply]]
! [[Filter (higher-order function)|filter]]
![[Fold (higher-order function)|fold]]
! sum
|-
|[[Python (programming language)|Python]]
|{{mono|lambda {{var|x}}: {{var|x}}}}
|{{mono|lambda {{var|args}}: expr}}
|{{mono|map(func, {{var|list}})}}
|{{mono|nfunc(*arguments)}}
|{{mono|filter(pred, {{var|list}})}}
|{{mono|functools.reduce(func2, {{var|list}})}}
|{{mono|sum({{var|list}})}}
|-
|[[Wolfram Mathematica|Mathematica]]
|{{mono|#&}}
|{{mono|(expr)&}} (arguments are {{mono|#1}}, {{mono|#2}}, etc.)
{{mono|Function[{''args''},expr]}}
|{{mono|Map[func, {{var|list}}]}}
{{mono|func /@ {{var|list}}}}
|{{mono|Apply[nfunc, {{var|args}}]}}
{{mono|nfunc@@args}}
|{{mono|Select[{{var|list}}, pred]}}
|{{mono|Fold[func2, val, {{var|list}}]}}
|{{mono|Apply[Plus,{{var|list}}]}}
{{mono|Plus@@{{var|list}}}}
|-
|[[C Sharp (programming language)|C#]]<ref name="enumerable" />
|{{mono|1=x => x}}
|{{mono|1=(args) => expr}}
| rowspan="2" |{{mono|Enumerable.Select({{var|list}}, func)}}
| rowspan="3" |Requires reflection
| rowspan="2" |{{mono|Enumerable.Where({{var|list}}, pred)}}
| rowspan="2" |{{mono|Enumerable.Aggregate({{var|list}}, func2)}}
{{mono|Enumerable.Aggregate({{var|list}}, val, func2)}}
| rowspan="2" |{{mono|Enumerable.Sum({{var|list}})}}
{{mono|Enumerable.Sum({{var|list}}, func)}}
|-
|[[Visual Basic .NET]]<ref name="enumerable" />
|{{mono|Function({{var|x}}) {{var|x}}}}
|{{mono|Function({{var|args}}) {{var|expr}}}}
|-
|[[F Sharp (programming language)|F#]]<ref name="seq" /> (can use Enumerable as well)
|{{mono|id}}(built-in)
{{mono|fun {{var|x}} -> {{var|x}}}}
|{{mono|fun pattern -> expr}}
|{{mono|Seq.map func {{var|list}}}}
|{{mono|Seq.filter pred {{var|list}}}}
|{{mono|Seq.fold func2 val {{var|list}}}}
|{{mono|Seq.sum {{var|list}}}}
{{mono|Seq.sumBy func {{var|list}}}}
|}

=== Numerical operations on lists ===
;{{mono|comp}}: a binary function that returns a value indicating sort order (an integer in most languages).

{| class="wikitable"
!
! sort
! max
! min
|-
| Python
|{{mono|sorted({{var|list}})}}
|{{mono|max({{var|list}})}}
|{{mono|min({{var|list}})}}
|-
| Mathematica
|{{mono|Sort[{{var|list}}]}}
|{{mono|Max[{{var|list}}]}}
|{{mono|Min[{{var|list}}]}}
|-
|C#<ref name="enumerable" />
| rowspan="2" |{{mono|Enumerable.OrderBy({{var|list}}, comp)}}
| rowspan="2" |{{mono|Enumerable.Max({{var|list}}, func)}}
| rowspan="2" |{{mono|Enumerable.Min({{var|list}}, func)}}
|-
|Visual Basic .NET<ref name="enumerable" />
|-
|F#<ref name="seq" />
|{{mono|Seq.sort {{var|list}}}}
{{mono|Seq.sortBy comp {{var|list}}}}
|{{mono|Seq.max}}
{{mono|Seq.maxBy func {{var|list}}}}
|{{mono|Seq.min}}
{{mono|Seq.minBy func {{var|list}}}}
|}

=== Iterations on lists ===

{| class="wikitable"
!
! group by
|-
| Python
|{{mono|itertools.groupby({{var|list}}, func)}}<ref name="itertools" />
|-
| Mathematica
|{{mono|GroupBy[{{var|list}}, func]}}<ref group="wolfram" name="GroupBy" />
|-
|C#<ref name="enumerable" />
| rowspan="2" |{{mono|Enumerable.GroupBy({{var|list}}, func)}}
|-
|Visual Basic .NET<ref name="enumerable" />
|-
|F#<ref name="seq" />
|{{mono|seq.groupBy func {{var|list}}}}
|}

=== Generating lists by combinatorics tools ===

;start: first value of range.
;step: increment of range.
;count: number of items in range.
;last: inclusive last value of range.
;end: exclusive last value of range.

{| class="wikitable"
!
! Generate range (lazily)
! Infinite range (lazily)
|-
| Python
|{{mono|xrange(start, end, step)}} (Python 2)<ref name="python2 builtins" />
{{mono|range(start, end, step)}} (Python 3)<ref name="python3 builtins" />
|{{mono|itertools.count(start, step)}}
|-
|C#<ref name="enumerable" />
| rowspan="2" |{{mono|Enumerable.Range(start, count)}}
| rowspan="2" |{{mono|Enumerable.Range(start, Int32.MaxValue)}}
|-
|Visual Basic .NET<ref name="enumerable" />
|-
|F#<ref name="seq" />
|{{mono|seq { start..step..last }}}
|{{mono|Seq.initInfinite func}}
|}

== References ==

{{reflist|refs=
<ref name="itertools">{{Cite web |url=https://docs.python.org/3/library/itertools.html#itertools |title=itertools — Functions creating iterators for efficient looping |website=Python 3.7.4 documentation |publisher=Python Software Foundation |access-date=2019-08-29}}</ref>
<ref name="python2 builtins">{{Cite web |url=https://docs.python.org/2/library/functions.html#xrange |title=Built-in Functions |website=Python 2.7.16 documentation |publisher=Python Software Foundation |access-date=2019-08-29}}</ref>
<ref name="python3 builtins">{{Cite web |url=https://docs.python.org/3/library/stdtypes.html#range |title=Built-in Types |website=Python 3.7.4 documentation |publisher=Python Software Foundation |access-date=2019-08-29}}</ref>
<ref name="enumerable">{{Cite web |url=https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable |title=Enumerable Class (System.Linq) |website=Microsoft Docs |publisher=Microsoft |access-date=2019-08-29}}</ref>
<ref name="seq">{{Cite web |url=https://msdn.microsoft.com/en-us/visualfsharpdocs/conceptual/collections.seq-module-%5bfsharp%5d |title=Collections.Seq Module (F#) |website=Microsoft Developer Network |publisher=Microsoft |access-date=2019-08-29}}</ref>
}}

{{reflist|group=wolfram|refs=
<ref name="GroupBy">{{Cite web |url=https://reference.wolfram.com/language/ref/GroupBy.html.en |title=GroupBy |website=Wolfram Language Documentation |publisher=Wolfram |access-date=2019-08-29}}</ref>
}}

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