* Implement signals for deleted variables etc.
* Sort out when small floats really are zero due to limited precision
* Quoted ")" in function
* Plot-functions
* Replace pointers to unit when unit type has changed (a different object must be created)
* Sort out percentile and provide alternative methods
* Return a range when appropriate for comparisons (ex. (2x-3)/(x-1)+x-3 > 0 => (x > 0 && x < 1, x > 2) instead of (x > 0, x > 2))

* More functions
* More units

* Increase support for non-glibc systems

* Sane and stable API
* API documentation

* Script/code plugins for advanced functions