Talk:First-class function: Difference between revisions

Revision as of 09:27, 1 October 2017

Revision as of 18:43, 11 May 2020

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IMO Python ''has'' unlimited function literals; it is possible to create any function (not limited to an expression like <tt>lambda</tt> functions) by creating a string and executing it; example:

<sourcesyntaxhighlight lang="python">

>>> code="""def myfunc(a):

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>>> myfunc(3.0)

3.0 is not an integer number

>>></sourcesyntaxhighlight>

(just tested using Python 2.5.2) --[[User:TobiasHerp|Tobias]] ([[User talk:TobiasHerp|talk]]) 09:55, 19 August 2008 (UTC)

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And what about this? ->

<sourcesyntaxhighlight lang="python">

import math

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# cos(math.pi/2) ~> 0.0

</syntaxhighlight>

</source>

== Regarding runtime generation ==

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== Higher-order functions in Perl ==

(see M.J. Dominus. Higher Order Perl, 2005. pp 325, 333)

<sourcesyntaxhighlight lang="perl">

$lambda = sub {$_[0] + 4};

print $lambda->(2), "\n"; # => 6

</syntaxhighlight>

</source>

[[User:Psilva|Psilva]] ([[User talk:Psilva|talk]]) 09:35, 26 September 2009 (UTC)

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In Python:

<sourcesyntaxhighlight lang="python">>>> def a(): pass

>>> def b(): pass

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{<function a at 0x0000000003266A48>, <function b at 0x00000000032669C8>}

>>> type({a, b})

<class 'set'></sourcesyntaxhighlight>

: In Haskell the keys of a map need to be of a finite type in order to guarantee that the the equality function will terminate (or more pessimistically, you cannot even define and equality function for functions in Haskell). The function type is infinite. Does Python compare function pointers? And does it work in combination with anonymous functions? —''[[User:Ruud Koot|Ruud]]'' 07:46, 17 February 2011 (UTC)

<sourcesyntaxhighlight lang="python">>>> a = lambda : None

>>> b = lambda : None

>>> type(a)

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False

>>> a is a

True</sourcesyntaxhighlight> --[[User:Paddy3118|Paddy]] ([[User talk:Paddy3118|talk]]) 08:36, 17 February 2011 (UTC)

It seems as if first classness of functions comes down to:

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: For your peace of mind: Python has first-class functions and reference equality:

<sourcesyntaxhighlight lang="python">

>>> def main():

... a = 10

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>>> (lambda x: x) == (lambda x: x)

False

</syntaxhighlight>

</source>

: —''[[User:Ruud Koot|Ruud]]'' 11:32, 17 February 2011 (UTC)

: Also Pythons nested functions seem crippled compared to Scheme:

<sourcesyntaxhighlight lang="python">

>>> def main():

... x = 1

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File "<stdin>", line 4, in f

UnboundLocalError: local variable 'x' referenced before assignment

</syntaxhighlight>

</source>

: but only artificially and not fatally:

<sourcesyntaxhighlight lang="python">

>>> def main():

... x = [1]

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>>> o()

5

</syntaxhighlight>

</source>

: —''[[User:Ruud Koot|Ruud]]'' 11:57, 17 February 2011 (UTC)

Hi Ruud, Python 3 addressed the access to outer variables issue with the nonlocal keyword:

<sourcesyntaxhighlight lang="python">Python 3.1 (r31:73572, Jun 28 2009, 18:34:47)

[GCC 3.3.4 (pre 3.3.5 20040809)] on linux2

Type "copyright", "credits" or "license()" for more information.

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>>> f()

4

>>> </sourcesyntaxhighlight> --[[User:Paddy3118|Paddy]] ([[User talk:Paddy3118|talk]]) 14:36, 17 February 2011 (UTC)

== Partial Function Application in C++ ==