Expression evaluator

The expression evaluator is due to Mark Morley. Some modifications have been
made, to add the possibility to evaluate objects. It is possible to use
the 4 operators `+,-, *, /` and parentheses. One can also define and use
variables, and use the usual mathematical functions.

Everything that is not recognized by the interpreter as a command or a program is supposed to be a numerical expression. It is computed and the result is printed on screen. For instance

- interpcom -> a=2 2.000000 - interpcom -> b=3 3.000000 - interpcom -> a+b 5.000000 - interpcom -> cos(a) -0.416147

It is possible to use numerical expressions as arguments of commands (or command files and programs) (cf. 7.6 and 6).

- Variables
- Functions
- User defined functions
- Objects
- Speed considerations
- Numerical expressions as arguments
- Additional expression evaluators

2009-11-12