1
分配在GHCI提示,不能在Haskell提示
我能夠做到的,
Prelude Text.Parsec> :t (oneOf "aeiou")
,並得到(oneOf "aeiou") :: Stream s m Char => ParsecT s u m Char
但是,當我這樣做,
let s = oneOf "aeiou"
I得到以下錯誤,
interactive>:36:9:
No instance for (Stream s0 m0 Char)
arising from a use of `oneOf'
Possible fix: add an instance declaration for (Stream s0 m0 Char)
In the expression: oneOf "aeiou"
In an equation for `m': m = oneOf "aeiou"
有人能告訴我爲什麼我不能分配給s?
也許是因爲類型違約。當你做'讓s =(oneOf「aeiou」):: Stream s m Char => ParsecT s?m Char'? – Satvik
[單態限制是什麼?](http://stackoverflow.com/questions/32496864/what-is-the-monomorphism-restriction) – Bakuriu