firsttrue

Format: firsttrue( a, b, ... )

Arguments: (bool) a, b, ... Any valid Boolean expressions

Returns: (text) Text of the argument that returned the first true value

Description: Firsttrue evaluates the expressions a, b, ... in that order and stops evaluating arguments as soon as one returns a true Boolean value. Firsttrue returns the expression that resulted in the true value.

This primitive is useful in constructing the root node in rule-based applications. Generally, a rule-based application's root node is of the form

Root:=firsttrue(Option1,Option2,...)

Option1, Option2, ... are names of branches that individually test the validity of competing options using rule sets.

Examples: First:=false

Second:=true

Third:=true

firsttrue(First,Second,Third) = Second

See Also: best, max, Logical And, Logical Or