groovy

Support for Closure composition

Details

  • Type: New Feature New Feature
  • Status: Closed Closed
  • Priority: Minor Minor
  • Resolution: Fixed
  • Affects Version/s: 1.8-beta-1
  • Fix Version/s: 1.8-beta-2
  • Component/s: None
  • Labels:
    None
  • Number of attachments :
    1

Description

It would be useful to support something like F#'s compose '>>' operator for Closures, e.g.:

def twice = { a -> a * 2 }
def inc = { b -> b + 1 }
def f = inc >> twice
def g = { x -> twice(inc(x)) } // longhand equivalent
assert f(10) == 22
assert g(10) == 22

def string2char = { it.chars[0] }
def p = Integer.&toHexString >> string2char >> Character.&toUpperCase
assert p(15) == 'F'

def multiply = { a, b -> a * b }
def identity = { a -> [a, a] }
def sq = identity >> multiply
assert (1..5).collect{ sq(it) } == [1, 4, 9, 16, 25]

Activity

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Paul King added a comment -

Proposed patch attached

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Paul King added a comment - Proposed patch attached
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Paul King added a comment -

Originally I had two variations. The current one:

f = g >> h
f = { h(g(it)) } // equivalent

And a "forced spreading" one:

f = g >>> h
f = { h(*g(it)) } // equivalent

but now I try to spread automatically if I can. If anyone can see a problem, let me know.

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Paul King added a comment - Originally I had two variations. The current one: f = g >> h f = { h(g(it)) } // equivalent And a "forced spreading" one: f = g >>> h f = { h(*g(it)) } // equivalent but now I try to spread automatically if I can. If anyone can see a problem, let me know.
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Paul King added a comment - - edited

Revised patch (includes fix for GROOVY-4336 which is required otherwise MixinTest breaks).

Patch now includes support for forward and reverse composition:

def times6 = { it * 2 } >> { it * 3 }
assert times6(3) == 18
assert { it * 2 } << { it * 3 } << 3 == 18
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Paul King added a comment - - edited Revised patch (includes fix for GROOVY-4336 which is required otherwise MixinTest breaks). Patch now includes support for forward and reverse composition: def times6 = { it * 2 } >> { it * 3 } assert times6(3) == 18 assert { it * 2 } << { it * 3 } << 3 == 18
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Guillaume Laforge added a comment -

Really looking forward to it, that's pretty powerful.
Patch looking good to me after a very quick glance only.

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Guillaume Laforge added a comment - Really looking forward to it, that's pretty powerful. Patch looking good to me after a very quick glance only.
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Paul King added a comment -

added

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Paul King added a comment - added

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  • Assignee:
    Paul King
    Reporter:
    Paul King
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  • Created:
    Updated:
    Resolved: