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Feature #6483

closed

parametric map

Added by prijutme4ty (Ilya Vorontsov) over 9 years ago. Updated about 9 years ago.

Status:
Rejected
Priority:
Normal
Target version:
[ruby-core:45198]

Description

I found very common use-case for map: map with parameters and &:meth syntax. For example:
matrix =1,2,3],[4,5,6
matrix.pmap(' ',&:join).join("\n") # => "1 2 3\n4 5 6
[1,2,3,4,5].pmap(2, &:to_s) # ['1', '10', '11', '100', '101']

[1,2,3,4,5].pmap(&:to_s) # ['1', '2, '3', '4', '5'] # empty parameter list behaves as usual map

Isn't it much better than ugly and verbose code:
matrix.map{|line| line.join(' ')}.join("\n")

I can write simple implementation
class Proc
def curry_except_self(*args)
Proc.new{|slf| curry[slf,*args] }
end
end

module Enumerable
def pmap!(*args,&block)
map! &block.curry_except_self(*args)
end
def pmap(*args,&block)
dup.pmap!(*args, &block)
end
end

Use-cases can be rewritten as tests (I can send my own unit-test if needed)

Also I've two related things to discuss.
1) First is &-syntax. Is it possible to change ruby-interpeter in such a way that &:proc could be at any place. matrix.pmap(&:join,' ') is much prettier than matrix.join(' ',&:join) What is the reason behind this restriction? And if one can remove this restriction, we'd have new nice syntax.
2) I'm not very experience in functional programming with curry etc, but it seems to me that currying proc without supplying first argument(self) can be common task when &:meth syntax is in play. If so, may be my curry_except_self(*args) also should be included in ruby.


Related issues

Related to Ruby master - Feature #4146: Improvement of Symbol and ProcRejectednobu (Nobuyoshi Nakada)Actions
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