String argument version

minor refactoring, add oneliners

Merge pull request #2 from bhmj/improve_variable_parser

variable bounds refined

Merge pull request #1 from bhmj/memory-optimization-v1

- Zero memory consumption on evaluation (preallocated on parse time)-
- Minor speed optimization
- infinity comparison improved
- invalid hex number detection
- test coverage report added

hex numbers support

variable can contain parentheses

de-optimization to fix revaluation

* revaluation fix

* SetLiteral() added

expression re-evaluation enabled