I have a package that takes a long list of boolean flags (currently about 10) in its options, and I want to test if exactly one of these is set to true - something like an XOR for 10+ booleans.
The only way I can think of is to use the ifthen package and construct a gigantic statement combining \and and \or to test this, but it quickly gets real ugly, and will be incredibly hard to maintain.
Is there a better way to do this?
You could create a counter, add one for each boolean that is true, then test if the counter has the value 1.
The question does not provide adequate information to provide an exact routine and as Willie Wong commented, it maybe trying to solve the problem with the wrong datastructure.
One approach is to place the booleans in a variable consisting of zeroes and ones. If anyone of the booleans is true then it will then be a number that is greater than zero.
\def\OneTrue#1{\ifnum#1<1 0\fi\number#1}
\OneTrue{1000101010}
One limitation of the macro above is that if the first boolean is 1 then the string can only be ten digits long, otherwise the number will be too big. Depending on the number of booleans one could extend the macro and split it into two to avoid this limitation and parse the two arguments.
What one does with it afterwards, it depends. One can actually use the first
boolean that is true to trigger another action. In such a case we would
have re-discovered the switch datastructure which is catered by ifcase in TeX!
\OneTrue macro. Do you want to test if at least one of the booleans is true? That's not what the OP wants.
Nov 20, 2010 at 9:28