Function approxEqAbs [src]

Performs an approximate comparison of two floating point values x and y. Returns true if the absolute difference between them is less or equal than the specified tolerance. The tolerance parameter is the absolute tolerance used when determining if the two numbers are close enough; a good value for this parameter is a small multiple of floatEps(T). Note that this function is recommended for comparing small numbers around zero; using approxEqRel is suggested otherwise. NaN values are never considered equal to any value.

Prototype

pub fn approxEqAbs(comptime T: type, x: T, y: T, tolerance: T) bool

Parameters

T: typex: Ty: Ttolerance: T

Example

 test approxEqAbs {
    inline for ([_]type{ f16, f32, f64, f128 }) |T| {
        const eps_value = comptime floatEps(T);
        const min_value = comptime floatMin(T);

        try testing.expect(approxEqAbs(T, 0.0, 0.0, eps_value));
        try testing.expect(approxEqAbs(T, -0.0, -0.0, eps_value));
        try testing.expect(approxEqAbs(T, 0.0, -0.0, eps_value));
        try testing.expect(!approxEqAbs(T, 1.0 + 2 * eps_value, 1.0, eps_value));
        try testing.expect(approxEqAbs(T, 1.0 + 1 * eps_value, 1.0, eps_value));
        try testing.expect(approxEqAbs(T, min_value, 0.0, eps_value * 2));
        try testing.expect(approxEqAbs(T, -min_value, 0.0, eps_value * 2));
    }

    comptime {
        // `comptime_float` is guaranteed to have the same precision and operations of
        // the largest other floating point type, which is f128 but it doesn't have a
        // defined layout so we can't rely on `@bitCast` to construct the smallest
        // possible epsilon value like we do in the tests above. In the same vein, we
        // also can't represent a max/min, `NaN` or `Inf` values.
        const eps_value = 1e-4;

        try testing.expect(approxEqAbs(comptime_float, 0.0, 0.0, eps_value));
        try testing.expect(approxEqAbs(comptime_float, -0.0, -0.0, eps_value));
        try testing.expect(approxEqAbs(comptime_float, 0.0, -0.0, eps_value));
        try testing.expect(!approxEqAbs(comptime_float, 1.0 + 2 * eps_value, 1.0, eps_value));
        try testing.expect(approxEqAbs(comptime_float, 1.0 + 1 * eps_value, 1.0, eps_value));
    }
}

Source

  pub fn approxEqAbs(comptime T: type, x: T, y: T, tolerance: T) bool {
    assert(@typeInfo(T) == .float or @typeInfo(T) == .comptime_float);
    assert(tolerance >= 0);

    // Fast path for equal values (and signed zeros and infinites).
    if (x == y)
        return true;

    if (isNan(x) or isNan(y))
        return false;

    return @abs(x - y) <= tolerance;
}  