I wonder if there is a possibility to use within GiNaC the C++ native precision arithmetic rather than that of CLN. In particular, following symbolic generation and manipulation of a mathematical model, it would be desirable in many cases to switch to machine arithmetic for numerical computations based on the tree of each constructed expression of interest. Such a possibility would obviate the need to spool external C++ source code, to recompile externally from the application built on GiNaC in the first place, and would lead to usability of GiNaC in limitless domains where eventual efficient numerical computation is paramount. Mathematica, although in a rudimentary and rather cumbersome way, has this option for example (the so-called compiled version of a function). Vassilis. ----------------------------------------------------------------- Dr. Vassilis S. Vassiliadis, Lecturer, UNIVERSITY OF CAMBRIDGE, DEPARTMENT OF CHEMICAL ENGINEERING Pembroke Street, Cambridge CB2 3RA, UK. Tel: (reception): +44 1223 334777 Fax: (departmental): +44 1223 334796 e-mail: vsv20@cheng.cam.ac.uk -----------------------------------------------------------------