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Contents
class Proc
# Returns a new proc that is the functional
# composition of two procs, in order.
#
# a = lambda { |x| x + 4 }
# b = lambda { |y| y / 2 }
#
# a.compose(b).call(4) #=> 6
# b.compose(a).call(4) #=> 4
#
# CREDIT Dave
def compose(g)
raise ArgumentError, "arity count mismatch" unless arity == g.arity
lambda{ |*a| self[ *g[*a] ] }
end
# Operator for Proc#compose and Integer#times_collect/of.
#
# a = lambda { |x| x + 4 }
# b = lambda { |y| y / 2 }
#
# (a * b).call(4) #=> 6
# (b * a).call(4) #=> 4
#
# CREDIT Dave
def *(x)
if Integer===x
# collect times
a = []; x.times{|i| a << call(i)}; a
else
# compose procs
lambda{|*a| self[x[*a]]}
end
end
# Use a Proc as an observable.
#
# CREDIT Tim Pease
alias_method :update, :call
end
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TestProc < Test::Unit::TestCase
def test_compose_op
a = lambda { |x| x + 4 }
b = lambda { |y| y / 2 }
assert_equal( 6, (a * b).call(4) )
assert_equal( 4, (b * a).call(4) )
end
def test_times_collect_op
a = lambda { |x| x + 4 }
assert_equal( [4,5,6], a * 3 )
end
def test_compose
a = lambda { |x| x + 4 }
b = lambda { |y| y / 2 }
assert_equal( 6, (a.compose(b)).call(4) )
assert_equal( 4, (b.compose(a)).call(4) )
end
end
=end
Version data entries
7 entries across 7 versions & 1 rubygems