BUG[?]: ΣLIST, ΠLIST with verrrry short lists

[parisse]

Inside giac, sigma list is implemented by initializing a variable of type giac::gen to 0, then the elements of the list are added to the variable. 0 + a string converts 0 to the string "0" then concatenate the string, so in some sense the CAS behavior was predictable. I don't see any real interest in modifying this, sigma list is not intended for strings.