5. Logical Operations

and
or
not

and

AND tf1 tf2 (AND tf1 tf2 tf3 ...)

outputs TRUE if all inputs are TRUE, otherwise FALSE. All inputs must be TRUE or FALSE. (Comparison is case-insensitive regardless of the value of CASEIGNOREDP. That is, true or True or TRUE are all the same.) An input can be a list, in which case it is taken as an expression to run; that expression must produce a TRUE or FALSE value. List expressions are evaluated from left to right; as soon as a FALSE value is found, the remaining inputs are not examined. Example:

MAKE "RESULT AND [NOT (:X = 0)] [(1 / :X) > .5]

to avoid the division by zero if the first part is false.

See section caseignoredp .

or

OR tf1 tf2 (OR tf1 tf2 tf3 ...)

outputs TRUE if any input is TRUE, otherwise FALSE. All inputs must be TRUE or FALSE. (Comparison is case-insensitive regardless of the value of CASEIGNOREDP. That is, true or True or TRUE are all the same.) An input can be a list, in which case it is taken as an expression to run; that expression must produce a TRUE or FALSE value. List expressions are evaluated from left to right; as soon as a TRUE value is found, the remaining inputs are not examined. Example:

IF OR :X=0 [some.long.computation] [...]

to avoid the long computation if the first condition is met.

See section caseignoredp .

not

NOT tf

outputs TRUE if the input is FALSE, and vice versa. The input can be a list, in which case it is taken as an expression to run; that expression must produce a TRUE or FALSE value.