String expressions
A string expression is an expression which results in a string. This includes string literals
and string variables. Here are valid string expressions:
"A character string" //A string literal
STRING(stringVar1) //where stringVar1 is a previously-declared string variable.
Only the string expressions can be assigned to string-type variables:
setStringVar2 SET(stringVar2, "A character string");
setStringVar2 SET(stringVar2, STRING(stringVar1));