Why3 Standard Library index

A mutable variable, or "reference" in ML terminology, is simply a record with a single mutable field [contents].

Creation, access, and assignment are provided as [ref], prefix [!], and infix [:=], respectively.

module Ref use export why3.Ref.Ref let function (!) (r: ref 'a) = r.contents let (:=) (ref r:'a) (v:'a) ensures { r = v } = r <- v end

a few operations specific to integer references

module Refint use int.Int use export Ref let incr (ref r: int) ensures { r = old r + 1 } = r <- r + 1 let decr (ref r: int) ensures { r = old r - 1 } = r <- r - 1 let (+=) (ref r: int) (v: int) ensures { r = old r + v } = r <- r + v let (-=) (ref r: int) (v: int) ensures { r = old r - v } = r <- r - v let ( *= ) (ref r: int) (v: int) ensures { r = old r * v } = r <- r * v end

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