Reply to @MarkMLI :

This is in fact a "real" question on the "mathematical functions" in Fpc-PASCAL. When you want to uses ArcTan2 for real calculation with a good precision for instance, we need to have more a 10**(-16) precision, to do it (numerical recipes in PASCAL) you have to tackkle many sources (as we did in Fortran) to be confident in the calculation method. The complex numbers formulations for Exp/Log need a "fine tuning" of the interval definitions for the trigonometric functions. Some functions like "de haar wavelets" or "Lanczos matrix calculations" can "explode" on the lake of accuracy, so we need the source with the unit ppu. Friendl. Yves .