Perform simple boolean (logical) computation.
Evaluate a plain boolean comparison storing the result into a variable:
eval <targetvariable> <booleancomparison>
Compute boolean and or or operation:
<booleaninstruction> <targetvariable> <booleancomparison>
Compute boolean not operation:
not <booleanvariable>
The <booleaninstruction> must be either and or or.
A <targetvariable> is defined as the identifier of a <variable> whose
value will be set to 1 or 0 depending on the boolean result 
true or false, respectively  yielded by the boolean
comparison or operation.
A <booleanvariable> is defined as the identifier of a <variable>
whose current value is a string representing a number, the boolean value
of which will be considered false if the number equals 0, true
if the number equals 1, or invalid otherwise.
A <booleancomparison> is defined as follows:
<comparisonvariable><comparisonoperator><comparisonvalue>
<comparisonvariable>
A <comparisonvariable> is the identifier of either a <variable>
or an <associativevariable>, possibly not set yet.
A <comparisonvalue> can be either a <variable>, or
a string of characters, possibly empty.
The <comparisonoperator> must be one of the following characters:
With the exception of comparison operator ~, that always
implies a patternmatching comparison between one string value and
a regular expression,
the type of comparison performed by Tefigel depends on the value of
<comparisonvariable> and
<comparisonvalue>: if both values are numerical, then a numerical
comparison takes place, otherwise a lexicographical comparison
is performed.
A <booleancomparison> with no <comparisonoperator>
and no <comparisonvalue> is assumed to be as follows:
<comparisonvariable>#0
[Previous chapter]
[Next chapter]
[Back to top]
