lib.div

This function is implemented in c++ and is part of the native nix runtime.

src/libexpr/primops.cc:4549

static void prim_div(EvalState & state, const PosIdx pos, Value ** args, Value & v)
{
    state.forceValue(*args[0], pos);
    state.forceValue(*args[1], pos);

    NixFloat f2 = state.forceFloat(*args[1], pos, "while evaluating the second operand of the division");
    if (f2 == 0)
        state.error<EvalError>("division by zero").atPos(pos).debugThrow();

    if (args[0]->type() == nFloat || args[1]->type() == nFloat) {
        v.mkFloat(state.forceFloat(*args[0], pos, "while evaluating the first operand of the division") / f2);
    } else {
        NixInt i1 = state.forceInt(*args[0], pos, "while evaluating the first operand of the division");
        NixInt i2 = state.forceInt(*args[1], pos, "while evaluating the second operand of the division");
        /* Avoid division overflow as it might raise SIGFPE. */
        auto result_ = i1 / i2;
        if (auto result = result_.valueChecked(); result.has_value()) {
            v.mkInt(*result);
        } else {
            state.error<EvalError>("integer overflow in dividing %1% / %2%", i1, i2).atPos(pos).debugThrow();
        }
    }
}