I'm building a custom expression parser and evaluator for production enviroment to provide a limited DSL to the users. The parser itself as the DSL, need to be simple. The parser is going to be built in an exotic language that doesn't support dynamic expression parsing nor has any parser generator tools available.

My decision is to go for recursive descent approach with LL(1) grammar, so that even programmers with no previous experience in evaluating expression could quickly learn how the code works.

It has to handle mixed expressions made up of several data types: decimals, percentages, strings and dates. And dates in the format of dd/mm/yyyy are easy to confuse with a string of devision ops.

Is where a good solution to this problem?

My own solution that is aimed at keeping the parser simple involves prefixing dates with a special symbol, let's say apostrophe:

<date>   ::= <apostr><digit><digit>/<digit><digit>/<digit><digit><digit><digit>

<apostr> ::= '

<digit>  ::= '0'..'9'