add of ceil()
minor improvements
bug fix of lambda-env
fix of wrong release
user defined unary minus operator
enable RTTI for list_
minor fix (canvas)
translate CR in reading files,
minor fixes: scrolling, line with NaN not drawn, allow STRING in imbalance() and serialize(), new_canvas
back to substitution-type marco for the time being,
and can break while loop in a macro.
eval in IF (for guard expression)
remove wrong error message
then clause should also be a statementList
prepare 3d canvas
definition of operators to value.h