Operators and Precedence

Operators like + and == are just functions with infix syntax.

Using an operator as a value

Parentheses turn an operator into a function value:

(+) 1 2

This enables partial application:

map ((*) 2) [1, 2, 3]

Operators come from type classes

Many operators are methods on prelude classes:

• + / zero from AdditiveMonoid
• * / one from MultiplicativeMonoid
• == / != from Eq
• ordering from Ord

This is why you can write + for both numbers and strings.

Precedence

Rex has a fixed precedence table (see Language Reference). A good habit is to use parentheses whenever you mix application with multiple infix operators.

(1 + 2) * 3

Record projection is not an operator

x.field is field projection syntax, not an operator you can partially apply:

type User = User { name: string }

let u: User = User { name = "Ada" } in u.name