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The const function is simple, but you can use it to make your code more legible. In this example we convert a unary function to a function of arity 2 (that ignores the second argument). Also by using the flip function from Haskell (which is equally easy to define) you can ignore the first argument.
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// [snippet:Declarations] // The const function let ct a _ = a // The flip function (not used in this snippet) let flip f x y = f y x // [/snippet] // [snippet:Use case] // Code taken from a toy interpreter type Exp = // ... // Lambdas are expressed as F# an function that takes a list of Exps and an env | Lambda of (Exp list -> Env -> Exp) // ... and Env = (string * Exp) list // Built-ins receive evaluated arguments so they don't care about the env. // By composing the function we get with ct we're basically converting a function // of arity 1 to a function of arity 2 that just ignores its second argument let builtin f = Lambda (f >> ct) // [/snippet]
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haskell functions
haskell functions
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