46:, which provides reflection facilities to support it. In general programming practice, however, this is considered poor style, and recursion with named functions is suggested instead. Anonymous recursion via explicitly passing functions as arguments is possible in any language that supports functions as arguments, though this is rarely used in practice, as it is longer and less clear than explicitly recursing by name.
343:
Even without mechanisms to refer to the current function or calling function, anonymous recursion is possible in a language that allows functions as arguments. This is done by adding another parameter to the basic recursive function and using this parameter as the function for the recursive call.
133:
The usual alternative is to use named functions and named recursion. Given an anonymous function, this can be done either by binding a name to the function, as in named function expressions in JavaScript, or by assigning the function to a variable and then calling the variable, as in function
352:
to this higher order function. This is mainly of academic interest, particularly to show that the lambda calculus has recursion, as the resulting expression is significantly more complicated than the original named recursive function. Conversely, the use of fixed-pointed combinators may be
134:
statements in JavaScript. Since languages that allow anonymous functions generally allow assigning these functions to variables (if not first-class functions), many languages do not provide a way to refer to the function itself, and explicitly reject anonymous recursion; examples include
115:
Anonymous recursion can also be used for named functions, rather that calling them by name, say to specify that one is recursing on the current function, or to allow one to rename the function without needing to change the name where it calls itself. However, as a matter of
49:
In theoretical computer science, anonymous recursion is important, as it shows that one can implement recursion without requiring named functions. This is particularly important for the
39:
features which allow one to access certain functions depending on the current context, especially "the current function" or sometimes "the calling function of the current function".
426:
Using a higher-order function so the top-level function recurses anonymously on an argument, but still needing the standard recursive function as an argument:
53:, which has anonymous unary functions, but is able to compute any recursive function. This anonymous recursion can be produced generically via
2729:
36:
977:
First make the higher-order function of two variables be a function of a single variable, which directly returns a function, by
74:
1827:
Combining these yields a recursive definition of the factorial in lambda calculus (anonymous functions of a single variable):
2743:, February 02, 2007, contains a substantially similar example found in the book above, but accompanied by more discussion.
353:
generically referred to as "anonymous recursion", as this is a notable use of them, though they have other applications.
28:
109:
105:
2014:
348:
allows anonymous recursion within the actual recursive function. This can be done purely anonymously by applying a
70:
2740:
2292:
outside a subroutine. This allows anonymous recursion, such as in the following implementation of the factorial:
135:
2413:
92:
is possible, such as by calling "the caller (the previous function)", or, more rarely, by going further up the
1410:
972:
349:
54:
2800:
2714:
702:
32:
141:
For example, in JavaScript the factorial function can be defined via anonymous recursion as such:
31:
which does not explicitly call a function by name. This can be done either explicitly, by using a
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592:
We can eliminate the standard recursive function by passing the function argument into the call:
89:
66:
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1091:
707:
117:
97:
85:
20:
84:
Anonymous recursion primarily consists of calling "the current function", which results in
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50:
101:
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2681:
Issue 226: It's impossible to recurse a anonymous function in Go without workarounds.
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2175:. These allow anonymous recursion, such as in this implementation of the factorial:
2025:. This allows anonymous recursion, such as in this implementation of the factorial:
78:
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2783:
2767:
2517:
It will not work, however, if passed as an argument to another function, e.g.
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93:
43:
1081:
There are two "applying a higher order function to itself" operations here:
970:, which only uses functions of a single variable, this can be done via the
356:
This is illustrated below using Python. First, a standard named recursion:
35:– passing in a function as an argument and calling it – or implicitly, via
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This creates a higher-order function, and passing this higher function
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Why was the arguments.callee.caller property deprecated in JavaScript?
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can be used. For example, the code below squares a list recursively:
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Get currently called function to write anonymous recursive function
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in the second. Factoring out the second double application into a
65:
Anonymous recursion is primarily of use in allowing recursion for
2281:
2018:
42:
In programming practice, anonymous recursion is notably used in
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token, which returns a reference to the current subroutine, or
104:
of "the current function" is a functional equivalent of the "
2521:, inside the anonymous function definition. In this case,
2788:
Can a lambda function call itself recursively in Python?
2772:
Can a lambda function call itself recursively in Python?
241:
Rewritten to use a named function expression yields:
2284:5.16, the current subroutine is accessible via the
1222:Factoring out the other double application yields:
1409:Combining the two combinators into one yields the
112:, allowing one to refer to the current context.
2171:, while the calling function is accessible via
701:The second line can be replaced by a generic
8:
16:Recursion without calling a function by name
2416:, the current function can be called using
2732:, p. 462—463. Derived substantially from
2167:, the current function is accessible via
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2717:, but it does appear in the following:
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1627:Expanding out the Y combinator yields:
2713:This terminology appear to be largely
96:, and this can be chained to produce
7:
2123:⍝ applied to each element of 0 to 9
14:
339:Passing functions as arguments
69:, particularly when they form
1:
120:this is generally not done.
110:object-oriented programming
2855:
2697:by olliej, Oct 25 '08 to "
2801:The 'current_sub' feature
2756:Deriving the Y combinator
2741:Anonymous Recursion in C#
2736:'s blog (see next item).
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55:fixed-point combinators
1085:in the first line and
350:fixed-point combinator
850:Written anonymously:
703:higher-order function
77:, to avoid having to
33:higher-order function
2768:Hugo Walter's answer
2758:, January 10th, 2008
2722:Accelerated C# 2008
67:anonymous functions
25:anonymous recursion
2803:", perldoc feature
2021:is accessible via
90:indirect recursion
2306:":5.16"
118:programming style
81:of the function.
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98:mutual recursion
86:direct recursion
21:computer science
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2297:#!/usr/bin/perl
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129:Named functions
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2799:Perldoc, "
2668:References
2165:JavaScript
2159:JavaScript
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258:factorial
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1938:lambda
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