I've got some code that does some string manipulation to assemble small equations, e.g. "(5+3)*8", and from these assembled strings I'd like to convert them to expressions for evaluation. This works in most circumstances, except when the string assembly produces something like "5--1", which should be read as "Five minus negative one". Instead, Mathematica's ToExpression function evaluates "--" as the Decrement function, which of course won't work since 5 is an integer, not a variable pointing to an integer that could be decremented.

Any thoughts on ways to change this behavior, apart from adding a space, e.g. "5- -1"?