When you try to differentiate a Maple expression with respect to one of the constituents (of expression) which is not simple atomic symbol, Maple could not perform operation, e.g. > diff( sin(x(t)), x(t)); Error, invalid input: diff received x(t), which is not valid for its 2nd argument . One solution to handle this problem is described in book (Maple book Chap.12)of Walter Ganz (Walter Ganz). In his trick structured symbol is temporarily replaced (via substitution) with a local variable, differentiation is performed with respect to local variable and finally local variable is replaced with original structured symbol.

Suppose you want to sort a list L ( of numbers ) and also determine order of elements as a list of indices corresponding to elements of original list L, that is, you want such a integer list "I" that "seq(L[I[j],j=1..nops(L))" to be equivalent to sorted list. This functionality is present in MATLAB in "[B,IX] = sort(...)" syntax and i come up with this problem while trying to convert a MATLAB function (GaussQuadratureWeights) to maple. The procedure described resolves problem using a few MAPLE commands including MAPLE's built-in sort function.