CODEWITHSUNDEEP
alloy
user3671603
user3671603

Reputation: 3

arithmetic operations in Alloy

I want to have a function for arithmetic operations in alloy, is it a good idea to define them in a fun as bellow?

sig expre{
    add: expre -> expre,
    sub: expre -> expre,
    mult: expre -> expre,
    div: expre -> expre,
    mod: expre -> expre,
    a: AttributeNames,
    val: Int
}

fun Exp(e: expre): Int{
     plus[e.val, e.val] + 
     minus[e.val, e.val] +
     mul[e.val, e.val] +
     div[e.val, e.val] +
     rem[e.val, e.val] +
     Exp[e]
}

Upvotes: 0

Views: 390

Answers (1)

Daniel Jackson
Daniel Jackson

Reputation: 2768

Not sure what you're trying to do, but it looks as if you might be looking to model a grammar of arithmetic expressions along with an evaluation function. If so, you're on the right track, but rather than defining the expression types as fields of a single signature, you probably want to define them as subsignatures:

abstract sig Expr { val: Int }
abstract sig UnaryExpr extends Expr { target: Expr }
abstract sig BinaryExpr extends Expr { left, right: Expr }
sig PlusExpr extends BinaryExpr { } {val = plus[left.@val, right.@val] }  
sig Literal extends Expr { }

Upvotes: 1

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