# calc1 - reverse-Polish calculator, version 1
#   input:  arithmetic expressions in reverse Polish
#   output: values of expressions

{   for (i = 1; i <= NF; i++)
        if ($i ~ /^[+-]?([0-9]+[.]?[0-9]*|[.][0-9]+)$/) {
            stack[++top] = $i
        } else if ($i == "+" && top > 1) {
            stack[top-1] += stack[top]; top--
        } else if ($i == "-" && top > 1) {
            stack[top-1] -= stack[top]; top--
        } else if ($i == "*" && top > 1) {
            stack[top-1] *= stack[top]; top--
        } else if ($i == "/" && top > 1) {
            stack[top-1] /= stack[top]; top--
        } else if ($i == "^" && top > 1) {
            stack[top-1] ^= stack[top]; top--
        } else {
            printf("error: cannot evaluate %s\n", $i)
            top = 0
            next
        }
    if (top == 1)
        printf("\t%.8g\n", stack[top--])
    else if (top > 1) {
        printf("error: too many operands\n")
        top = 0
    }
}