uniform half4 colorGreen, colorRed;

half4 main(float2 coords) {
    float4 value                  = float4(2.5, -2.5, 8, -0.125);
    const float4 expectedWhole    = float4(2,   -2,   8, 0);
    const float4 expectedFraction = float4(0.5, -0.5, 0, -0.125);
    bool4  ok = bool4(false);
    float4 whole, fraction;

    fraction.x    = modf(value.x,    whole.x);
    ok.x          = whole.x    == expectedWhole.x    && fraction.x    == expectedFraction.x;
    fraction.xy   = modf(value.xy,   whole.xy);
    ok.y          = whole.xy   == expectedWhole.xy   && fraction.xy   == expectedFraction.xy;
    fraction.xyz  = modf(value.xyz,  whole.xyz);
    ok.z          = whole.xyz  == expectedWhole.xyz  && fraction.xyz  == expectedFraction.xyz;
    fraction.xyzw = modf(value.xyzw, whole.xyzw);
    ok.w          = whole.xyzw == expectedWhole.xyzw && fraction.xyzw == expectedFraction.xyzw;

    return all(ok) ? colorGreen : colorRed;
}