value-restriction | 易学教程

Keeping partially applied function generic

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问题 Is it possible to partially apply a function such as bprintf and prevent it from being restricted based on its initial use? I'd like to do the following: let builder = new System.Text.StringBuilder() let append = Printf.bprintf builder append "%i" 10 append "%s" string_value 回答1: you can add explicit format argument let builder = new System.Text.StringBuilder() let append format = Printf.bprintf builder format append "%i" 10 append "%s" "1" 回答2: The aspect of F# that's causing this is called

Understanding F# Value Restriction Errors

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I don't understand how the Value Restriction in F# works. I've read the explanation in the wiki as well as the MSDN documentation . What I don't understand is: Why, for example, this gives me a Value Restriction error (Taken from this question): let toleq (e:float<_>) a b = (abs ( a - b ) ) < e But ths doesn't: let toleq e (a:float<_>) b = (abs ( a - b ) ) < e This is generalized all right... let is_bigger a b = a < b but this isn't (it is specified as int): let add a b = a + b Why functions with implicit parameters generate Value Restriction: this: let item_count = List.fold (fun acc _ -> 1 +

Understanding F# Value Restriction Errors

阅读更多关于 Understanding F# Value Restriction Errors

问题 I don\'t understand how the Value Restriction in F# works. I\'ve read the explanation in the wiki as well as the MSDN documentation. What I don\'t understand is: Why, for example, this gives me a Value Restriction error (Taken from this question): let toleq (e:float<_>) a b = (abs ( a - b ) ) < e But ths doesn\'t: let toleq e (a:float<_>) b = (abs ( a - b ) ) < e This is generalized all right... let is_bigger a b = a < b but this isn\'t (it is specified as int): let add a b = a + b Why