/* iGASM example */
/* Tokenizes strings of expressions with binary operators */
UNIVERSES 
        Operator = {"+","-","*","/","(",")"};  /* available operators */
FUNCTIONS
        tape : List;       /* resulting list of lexems */
        str      : String; /* auxiliary string */
        instr    : String; /* input string */
        counter : Number;  /* string index */

INITIAL 
        tape       := emptyList;
        str  := "";
        counter := 0;
        instr := readln("Enter an expression");

FINAL counter = undef;

RULES
  if counter<size(instr) then
    counter := counter+1;
    if Operator(toString(strCharAt(instr, counter))) then
      str  := "";
      IF str != "" THEN
        tape := listAppend( listAppend(tape, toNumber(str)),
                       toString(strCharAt(instr, counter)));
      ELSE
        tape := listAppend( tape, toString(strCharAt(instr, counter)));
      ENDIF
    ELSE
      str := str + toString(strCharAt(instr, counter));
    endif
  else
    if str!="" then
      tape := listAppend(tape, toNumber(str));
    endif
    counter := undef;
    writeln := listAppend(tape, toNumber(str));
  endif