TclODE is a solver for Ordinary Differential Equations that is tightly integrated with the Tcl programming language.
TclODE is based on the popular ODEPACK solvers, originally developed at Lawrence Livermore National Laboratory. In particular, it uses an automatic C translation of the Fortran codes produced by the f2c compiler, postprocessed with a Tcl script that modifies the generated C code to attend to thread-safety and re-entrancy issues.
Tcl/Tk