From: Raffaele Vitolo <raffaele.vitolo@un...>  20111027 14:02:33

Dear All, I should solve a system of equations where a set of variables are substituted by expressions which, in turn, can contain variables from the same set to be substituted. This does not lead me to 'circular' substitutions or to new conditions because of some theoretical principles under which the system is built. Substitutions are implemented as a sequence of `let a=b' rules. However, it seems to me that the number of these substitutions slows down the computation too much. So, my question is if there exists a way (like an internal parameter) to measure the number of nested substitutions and/or a faster way to do substitutions than `let' rules, such as a way to get rid of nested substitutions before using substitutions in computations. Best regards, Raffaele.  Raffaele Vitolo, Dipartimento di Matematica 'E. De Giorgi' Universita' del Salento, via per Arnesano 73100 Lecce ITALY tel.: +39 0832 297425 (office) fax.: +39 0832 297594 home page: http://poincare.unisalento.it/vitolo 