to get a program to return EXPR("%{1,2,3,3,4%}") as the set [1,2,3,4]

[Han]

The CAS() command is intended to provide users with access to the CAS environment as well as the CAS commands. It is, however, a "Home" command which means the "Home" environment rules are applied. Generally speaking, this means that all referenced variables were passed as resolved values. For example, if x:=2 and we subsequently called a routine using: MYPROG(x), then 2 is passed in place of x. This method, however, caused problems for symbolic computations in which it is sometimes necessary to pass arguments unevaluated.

In much older firmwares, the CAS() command would always resolve all variables first before passing control over to the CAS environment. In the newer firmwares, all variables passed to CAS() are left as-is (to be resolved from the CAS environment). In order to pass resolved values, we use EVAL().