4.9 Substitutions

For substituting kernels in standard forms or standard quotients by other kernels or arbitrary algebraic expressions the following functions are available :

where a is a list of pairs, each with a kernel to be replaced in the car and its replacement as algebraic form in the cdr ¹³, e.g.

Here x is replaced by 5 while y is replaced by a + b.

Note that

• both subf and subsq return a standard quotient (the substitution might have caused a non trivial denominator),
• subf and subsq also introduce substitutions which have been coded in rules - so it makes sense to call these routines with nil as the second argument if you have introduced a new rule and some standard forms or standard quotients need to be re simplified under these.