Call a function: Difference between revisions

=={{header|Lambdatalk}}==

In lambdatalk functions are abstractions {lambda {args} body} whose behaviour is best explained as a part of such a complete expression {{lambda {args} body} values}.

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The command

replace :a0 :a1 ... an-1

in expression containing some occurences of :ai

by v0 v1 ... vp-1

is rewritten in a prefixed parenthesized form

{{lambda {:a0 :a1 ... an-1}

expression containing some occurences of :ai}

v0 v1 ... vp-1}

so called IIFE (Immediately Invoked Function Expression), and defines an anonymous function containing a sequence of n arguments :ai, immediately invoked on a sequence of p values vi, and returning the expression in its body as so modified:

1) if p < n (partial application)

• the occurrences of the p first arguments are replaced in the function's body by the corresponding p given values,

• a function waiting for missing n-p values is created,

• and its reference is returned.

• example:

{{lambda {:x :y} ... :y ... :x ...} hello}

-> {lambda {:y} ... :y ... hello ...} // replaces :x by hello

-> LAMB_123 // the new functions's reference

• called with the value world this function will return ... world ... hello ...

2) if p = n (normal application)

• the occurences of the n arguments are replaced in the function's body by the corresponding p given values,

• the body is evaluated and the result is returned.

• example

{{lambda {:x :y} ... :y ... :x ...} hello world}

-> {{lambda {:y} ... :y ... hello ...} world} // replaces :x by hello

-> {{lambda {} ... world ... hello ...} } // replaces :y by world

-> ... world ... hello ... // the value

3) if p > n (variadicity)

• the occurrences of the n-1 first arguments are replaced in the function's body by the corresponding n-1 given values,

• the occurrences of the last argument are replaced in the body by the sequence of p-n supernumerary values,

• the body is evaluated and the result is returned.

• example:

{{lambda {:x :y} ... :y ... :x ...} hello world good morning}

-> {{lambda {:y} ... :y ... hello ...} world good morning}

-> {{lambda {} ... world good morning ... hello ...}}

-> ... world good morning ... hello ... // the value

More can be seen in http://lambdaway.free.fr/lambdawalks/?view=lambda

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