Haskell做符号绑定 [英] Haskell do notation to bind
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问题描述
只有我能想到的是一个沉重的嵌套let语句,看起来相当难看。
语句应该用bind替换: p>
do num < - numberNode x
nt1 < - numberTree t1
nt2 < - numberTree t2
return(节点号nt1 nt2)
任何输入值得高度赞赏=)
解决方案
numberNode x>> = \ num - >
numberTree t1>> = \\\
t1 - >
numberTree t2>> = \\\
t2 - >
return(Node num nt1 nt2)
请注意,如果您使用Applicatives,则更简单:
节点< $> numberNode x * numberTree t1 * numberTree t2
I´am trying to desugar a do statement in Haskell. I have found some examples here on SO but wasn´t able to apply them to my case. Only thing I can think of is a heavy nested let statement, which seems quite ugly.
Statement in which do notation should be replaced by bind:
do num <- numberNode x
nt1 <- numberTree t1
nt2 <- numberTree t2
return (Node num nt1 nt2)
Any input is highly appreciated =)
解决方案
numberNode x >>= \num ->
numberTree t1 >>= \nt1 ->
numberTree t2 >>= \nt2 ->
return (Node num nt1 nt2)
Note that this is simpler if you use Applicatives:
Node <$> numberNode x <*> numberTree t1 <*> numberTree t2
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