dunitconversion.linearfunction source code

1 module dunitconversion.linearfunction;
2 
3 import std.math;
4 
5 /**
6  * The LinearFunction class describes a linear function
7  * with a format of Y = k*X + b
8  */
9 struct LinearFunction {
10 
11     @disable this();
12 
13     /**
14      * Constructor
15      * Params:
16      *      k = K factor value
17      *      b = bias value
18      */
19     this (double k, double b) {
20         this.k = k;
21         this.b = b;
22     }
23 
24     /**
25      * Checks if linear function is valid, i.e. if k != 0
26      * Returns: `true` if function is valid, `false` otherwise
27      */
28     bool isValid() const nothrow {
29         return !approxEqual(k, 0);
30     }
31 
32     /**
33      * Reverses current linear function so X = k*Y + b
34      * Returns: an object of type QLinearFunction containing inversed function
35      * Details: This function doesn't perform validity check so applying it to
36      * invalid function will cause division by zero
37      */
38     LinearFunction inversed() const {
39         if (!isValid())
40             throw new Exception("Can't inverse non-valid function");
41         return LinearFunction(1. / k, -b / k);
42     }
43 
44     /**
45      * Function value
46      * Params: x = function argument
47      * Returns: value of a function with an argument `x`
48      */
49     double y(double x) const {
50         return k * x + b;
51     }
52 
53     double k;   /// Function scale factor K
54     double b;   /// Function bias b
55 }