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5. Logical Operations


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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 .


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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 .


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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.


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This document was generated by Brian Harvey on September, 3 2008 using texi2html 1.78.