题
我需要实现在红宝石咖喱功能(1.8.6或1.8.7不1.9)的一些示例。
解决方案
因此,这里是如何做到与块讨好,而不是方法:
def curry(&block)
arity = (block.arity >= 0) ? block.arity : -(block.arity + 1)
# return an immediate value if the block has one
return block[] if arity == 0
# otherwise, curry it argument by argument
args = []
innermost = lambda do |last,*extra|
args[arity-1] = last
block[*(args+extra)]
end
(0...(arity-1)).to_a.reverse.inject(innermost) do |inner,i|
lambda do |arg_i,*extra|
args[i] = arg_i
# pass extra arguments on to inner calls
if extra.empty?
inner
else
inner[*extra]
end
end
end
end
和它的作品相当不错的做法。参数可以令行禁止或没有, 额外的参数被收集照例:
irb> (curry { |x,y| x + y })[1,2]
#=> 3
irb> (curry { |x,y| x + y })[1][2]
#=> 3
irb> (curry { |x,*ys| ys << x })[1]
#=> [1]
irb> (curry { |x,*ys| ys << x })[1,2,3]
#=> [2, 3, 1]
irb> (curry { |x,y,*zs| zs << (x+y) })[1,2]
#=> [3]
irb> (curry { |x,y,*zs| zs << (x+y) })[1,2,4]
#=> [4, 3]
irb> (curry { |x,y,*zs| zs << (x+y) })[1][2]
#=> [3]
irb> (curry { |x,y,*zs| zs << (x+y) })[1][2,4]
#=> [4, 3]
irb> (curry { |a,b,c,d,e| a+b+c+d+e })[1,2,3,4,5]
#=> 15
irb> (curry { |a,b,c,d,e| a+b+c+d+e })[1][2][3][4][5]
#=> 15
irb> (curry { |a,b,c,d,e| a+b+c+d+e })[1,2][3][4][5]
#=> 15
irb> (curry { |a,b,c,d,e| a+b+c+d+e })[1][2,3,4][5]
#=> 15
我作出的设计决策已经没有精氨酸块上讨好返回一个立即值:
irb> curry { 3 }
#=> 3
irb> curry { |*xs| xs }
#=> []
这是必要的,以避免不得不结束与[]
每次讨好(和相当的Haskell样)。
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