Module Arithmetic

module Arithmetic: sig .. end

This module defines an expression type for manipulating simple arithmetic expressions. The expressions are given by the type exp and the main operation defined is fold, which generalizes List.fold_right to the exp type.

type exp =

`\|`	`Val of int`	`(*`	The `Val` constructor represents primitive integers.	`*)`
`\|`	`Plus of exp * exp`	`(*`	The `Plus` constructor represents expressions of the form `x + y`.	`*)`
`\|`	`Times of exp * exp`	`(*`	The `Times` constructor represents expressions of the form `x * y`.	`*)`

The exp type is the type abstraction for arithmetic expressions.

val exp_fold : (int -> 'a) -> ('a -> 'a -> 'a) -> ('a -> 'a -> 'a) -> exp -> 'a

The expression fold val_op plus_op times_op exp recursively processes each sub-expression of exp via the following scheme:

It applies the operation val_op to each Val sub-expression.
It applies the operation plus_op to each Plus sub-expression.
It applies the operation times_op to each Times sub-expression

val eval : exp -> int

The eval function takes an input expression and evaluates it according the rules of ordinary integer arithmetic.

val to_string : exp -> string

to_string exp return a fully parenthesized string representation of exp with no spaces between operators and their operands.