8.1. Boolean

A boolean is either true or false. A boolean can be represented by an i1 in MLIR.

8.1.1. Declaration

A boolean value is declared with the keyword boolean. If the variable is not initialized explicitly, it is set to false (its zero value).

8.1.2. Literals

The following are the only two valid boolean literals:

true
false

8.1.3. Operations

The following operations are defined on boolean values. In all of the usage examples bool-expr means some boolean yielding expression.

Operation	Symbol	Usage
parentheses	`()`	`(bool-expr)`
negation	`not`	`not bool-expr`
logical or	`or`	`bool-expr or bool-expr`
logical xor	`xor`	`bool-expr xor bool-expr`
logical and	`and`	`bool-expr and bool-expr`
equals	`==`	`bool-expr == bool-expr`
not equals	`!=`	`bool-expr != bool-expr`

Unlike many languages, the and and or operators do not use short-circuit evaluation. Therefore, both the left hand side and right hand side of an expression must always be evaluated. This has a practical consequence: a guard like x != 0 and 1/x > 0 does not protect the division – 1/x is evaluated even when x is 0, raising a MathError (see Integer and Errors). To guard a fallible expression, nest an if instead.

Operator precedence and associativity are specified once, for all types, in the table of operator precedence.

8.1.4. Type Casting and Implicit Casts

To see the types that boolean may be cast and/or implicitly cast to, see the sections on Type Casting and Implicit Casts respectively.