Name Rascal/Expressions/Values/Boolean/Or

Synopsis The or operator on Boolean values.

Syntax Exp1 || Exp2

Types

Exp1	Exp2	Exp1 || Exp2
bool	bool	bool

Description The or operator on Boolean values defined as follows:

Exp1	Exp2	Exp1 || Exp2
true	true	true
true	false	true
false	true	true
false	false	false

Boolean operators have short circuit semantics: only those operands are evaluated that are needed to compute the result. In the case of the || operator, the result is true if Exp1 evaluates to true, otherwise Exp2 is evaluated to determine the result.

Note that || will backtrack over its argument expressions until it can find an evaluation that is true, unless there is none.

Variable assignments as a result of matching or generator expressions under a || are visible outside the context of the operator, but only if the context is conditional, such as an if-then-else or a for loop. Note that it is statically required that both sides of an || introduce the same variable names of the same type.

Examples

rascal>import IO;
ok
rascal>false || true;
bool: true
rascal>(i <- [1,2,3,4] && i % 2 == 0) || false
bool: true
rascal>for ((i <- [1,2,3,4] && i % 2 == 0) || false) 
>>>>>>>  println("true for <i>");
true for 2
true for 4
list[void]: []

[Edit] | [New Subconcept] | [Recompile Course] | [Warnings]