package expr

import (
    `fmt`
)

func idiv(v int64, d int64) (int64, error) {
    if d != 0 {
        return v / d, nil
    } else {
        return 0, newRuntimeError("division by zero")
    }
}

func imod(v int64, d int64) (int64, error) {
    if d != 0 {
        return v % d, nil
    } else {
        return 0, newRuntimeError("division by zero")
    }
}

func ipow(v int64, e int64) (int64, error) {
    mul := v
    ret := int64(1)

    /* value must be 0 or positive */
    if v < 0 {
        return 0, newRuntimeError(fmt.Sprintf("negative base value: %d", v))
    }

    /* exponent must be non-negative */
    if e < 0 {
        return 0, newRuntimeError(fmt.Sprintf("negative exponent: %d", e))
    }

    /* fast power first round */
    if (e & 1) != 0 {
        ret *= mul
    }

    /* fast power remaining rounds */
    for e >>= 1; e != 0; e >>= 1 {
        if mul *= mul; (e & 1) != 0 {
            ret *= mul
        }
    }

    /* all done */
    return ret, nil
}