c# - How does modulus operation works with float data type?

Question

I m trying to find out a simple modulus operation on float data type.

float a=3.14f;
float b=10f;
result=a%b;

I m getting result= 3.14

Another example using decimal data types:

decimal p=10;
decimal q=40;
result=p%q;

getting answer=20.

I am not understanding how does modulus works?

Answer 1

From the C# language spec on floating point remainder. In the case of x % y if x and y are positive finite values.

z is the result of x % y and is computed as x – n * y, where n is the largest possible integer that is less than or equal to x / y.

The C# language spec also clearly outlines the table of what to do with the cases of all possible combinations of nonzero finite values, zeros, infinities, and NaN’s which can occur with floating point values of x % y.

                          y value

                | +y  –y  +0  –0  +∞  –∞  NaN
           -----+----------------------------  
  x         +x  | +z  +z  NaN NaN x   x   NaN
            –x  | –z  –z  NaN NaN –x  –x  NaN
  v         +0  | +0  +0  NaN NaN +0  +0  NaN
  a         –0  | –0  –0  NaN NaN –0  –0  NaN
  l         +∞  | NaN NaN NaN NaN NaN NaN NaN
  u         –∞  | NaN NaN NaN NaN NaN NaN NaN
  e         NaN | NaN NaN NaN NaN NaN NaN NaN