48 lines
2.1 KiB
Plaintext
48 lines
2.1 KiB
Plaintext
The command
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replace :a0 :a1 ... an-1
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in expression containing some occurences of :ai
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by v0 v1 ... vp-1
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is rewritten in a prefixed parenthesized form
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{{lambda {:a0 :a1 ... an-1}
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expression containing some occurences of :ai}
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v0 v1 ... vp-1}
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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:
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1) if p < n (partial application)
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• the occurrences of the p first arguments are replaced in the function's body by the corresponding p given values,
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• a function waiting for missing n-p values is created,
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• and its reference is returned.
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• example:
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{{lambda {:x :y} ... :y ... :x ...} hello}
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-> {lambda {:y} ... :y ... hello ...} // replaces :x by hello
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-> LAMB_123 // the new functions's reference
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• called with the value world this function will return ... world ... hello ...
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2) if p = n (normal application)
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• the occurences of the n arguments are replaced in the function's body by the corresponding p given values,
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• the body is evaluated and the result is returned.
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• example
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{{lambda {:x :y} ... :y ... :x ...} hello world}
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-> {{lambda {:y} ... :y ... hello ...} world} // replaces :x by hello
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-> {{lambda {} ... world ... hello ...} } // replaces :y by world
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-> ... world ... hello ... // the value
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3) if p > n (variadicity)
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• the occurrences of the n-1 first arguments are replaced in the function's body by the corresponding n-1 given values,
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• the occurrences of the last argument are replaced in the body by the sequence of p-n supernumerary values,
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• the body is evaluated and the result is returned.
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• example:
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{{lambda {:x :y} ... :y ... :x ...} hello world good morning}
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-> {{lambda {:y} ... :y ... hello ...} world good morning}
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-> {{lambda {} ... world good morning ... hello ...}}
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-> ... world good morning ... hello ... // the value
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More can be seen in http://lambdaway.free.fr/lambdawalks/?view=lambda
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