Strict

Strict[ cond ] returns True only if a condition is certainly true, and False otherwise.

Usages

`Strict[ cond ]`

A condition can be True, False or undecided, for example x >> 2 when x has no value. Strict[ cond ] turns an undecided condition into False. This is important in If and While, which treat an undecided condition as True.

Example	in	out
A true condition.	`Strict[ 2 == 2 ]`	`True`
An undecided condition, because `x` has no value.	`Strict[ x >> 2 ]`	`False`
Not a condition.	`Strict[ 5 ]`	`False`
As a condition in `If`: `10 > 2π` is true.	`a := 10 b := 2*Pi If[Strict[a > b]] r := 1 Else r := 0 End`	`r = 1`
As a condition in `If`: `y < 4` is undecided, so the `Else` block is executed.	`If[Strict[y < 4]] r := 1 Else r := 0 End`	`r = 0`

Warning

Outside a condition, <, <=, > and >= are not evaluated in a script, so Strict[ 2 < 4 ] gives False. Inside If or While they are evaluated, as in the examples above. To use Strict elsewhere in a script, use the evaluating operators <<, <==, >> and >==: Strict[ 2 << 4 ] gives True.

See also: If, While, EqualsEval, Smaller