/* A simple calculator.
 *
 * Accepts expressions of the form:
 *   1+1
 *   2*3-4
 *   (5+6)/7
 *   etc
 *
 * [Ant 19/10/2002]
 */

manycalcs =
  [ "\n", "calc", [],
    [ "fail", "calc" ] ];

calc =
  [ "read_prefix", [[], 0], "expr",
    [ "script",
      [ "declare", "a" ],
      [ "setparas", ["a"] ],
      [ "later", "writeln('=',%%);", "a" ] ],
    [ "fail", "calc_err" ] ];

func op_expr {
  para op, next;
  return 
    [ "pivot", op,
      [ "expr", "expr" ],
      [ "ignore", ["bras"] ],
      [ "script",
        [ "declare", "a", "b" ],
        [ "setparas", ["a"], ["b"] ],
        [ "execute", "%% is %% " // op // " %%;", "v_paras[1]", "a", "b" ] ],
      [ "fail", next ] ];
}

expr = op_expr("+", "expr2");
expr2 = op_expr("-", "expr3");
expr3 = op_expr("/", "expr4");
expr4 = op_expr("*", "expr5");

expr5 =
  [ "prefix", "(", "expr6",
    [ "script",
      [ "setparas", ["v_paras[1]"] ] ],
    [ "fail", "term" ] ];

expr6 =
  [ "suffix", ")", "expr",
    [ "script",
      [ "setparas", ["v_paras[1]"] ] ] ];

term =
  [ "read_all", [["0","9"]],
    [ "script",
      [ "later", "%% = $$;", "v_paras[1]", "v_substrs[1]" ] ] ];

calc_err =
  [ "read_all", [],
    [ "script",
      [ "execute", "writeln('calc: syntax error');" ] ] ];

installAOP("%calc","manycalcs");