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

[John P]

Hello,
Does somebody know how to change list to a set. I am trying to get a program to return EXPR("%{1,2,3,3,4%}") as the set [1,2,3,4], but the program when it comes to EXPR("%{1,2,3,3,4%}") gives me "Error: Syntax Error". When I do not use EXPR I get "%{1,2,3,3,4%}" and outside the prgm. when I use EXPR("%{1,2,3,3,4%}") I get the set [1,2,3,4]. The problem is; how to get the program to return the set [1,2,3,4] instead giving me "Error: Syntax Error" when using EXPR.

Thank you,
John P