Standard | 0-1 Rainbow Function

/*
    A function that outputs an RGBA colour when given a value between 0 and 1
     (inc/decrementing the value for "cycle" passed will cycle through the rainbow)
    You can also define a range to which the output colour is scaled and clamped
     (useful if you want to cycle through dark/pastel/greyed rainbow colours instead of pure, e.g.)
       minVal | maxVal | RESULT
       0.0    | 256.0  | Colours are fully saturated
       128.0  | 256.0  | Colours are semi-saturated into white; pastel colours
       0.0    | 128.0  | Colours are semi-saturated into black; darkened colours
       96.0   | 144.0  | Colours are distinctly greyed
       256.0  | 256.0  | Colour will just be white, what are you doing
       0.0    | 0.0    | Now it's just gone completely black, stop this nonsense
       128.0  | 128.0  | Something tells me you're not doing this properly
*/

// Need "math.h" for math functions ("cmath" should also be fine, but blegh)
#include <math.h>

// Placeholder colour structure
struct Colour
{
    Colour():r(255),g(255),b(255),a(255){};
    Colour(int r,int g,int b,int a=255):r(r),g(g),b(b),a(a){};
    int r; int g; int b; int a;
}

Colour Rainbow(double cycle, int alpha=255, double minVal=0.0, double maxVal=255.0)
// "alpha" is alpha of output colour,
// "minVal" and "maxVal" define a range to which the output colour is scaled and clamped
{
    // ensure that "cycle" is rotated to a value within [0 <= cycle < 1]
    if(cycle<0.0||cycle>=1.0) cycle=cycle-floor(cycle);
    // ensure that "alpha" is a value within [0 <= alpha <= 255]
    alpha=(alpha<0?0:(alpha>255?255:alpha));
    // ensure that "minVal" is the smallest of itself and "maxVal"
    if(minVal>maxVal){ minVal=minVal-maxVal; maxVal=maxVal+minVal; minVal=maxVal-minVal; }
    // ensure that "minVal" is [>=0] and "maxVal" is [<=255]
    minVal=(minVal<0?0:minVal); maxVal=(maxVal>255?255:maxVal);

    // get each of r, g and b given the current value of "cycle"
    double r = (maxVal-minVal)*(abs((1.0/2.0 - c)*6.0) - 1.0)+minVal;
    double g = (maxVal-minVal)*(2.0 - abs((1.0/3.0 - c)*6.0))+minVal;
    double b = (maxVal-minVal)*(2.0 - abs((2.0/3.0 - c)*6.0))+minVal;
    // ensure they're clamped between the minimum and maximum values
    r = (r<minVal?minVal:(r>maxVal?maxVal:r));
    g = (g<minVal?minVal:(g>maxVal?maxVal:g));
    b = (b<minVal?minVal:(b>maxVal?maxVal:b));

    // To output for another format, rewrite this line and change the return type as necessary
    return Colour( static_cast<int>(r), static_cast<int>(g), static_cast<int>(b), alpha );
}