A switch case example as below. The expression used in switch must be integral type ( int, char and enum). Any other type of expression is not allowed. Why?
int main()
{
int x = 2;
switch (x)
{
case 1: printf("Choice is 1\n");
case 2: printf("Choice is 2\n");
case 3: printf("Choice is 3\n");
default: printf("Choice other than 1, 2 and 3\n");
}
return 0;
}
My best guess is it is because floating point values are inherently not precise. Switch statements are all about precise matching. Using real number types in a switch is potentially troublesome because in a computer, real numbers (floating point) are approximations (very precise approximations, but approximations nonetheless).
There are lots of articles out there which explain why comparing floats/doubles for exact equality is usually a mistake. Especially if the comparison is of the results of calculations. See for example:
Comparing Floating Point Numbers, 2012 Edition
https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
Note the section: "Comparing for equality".
Floating point number representation
http://www.cprogramming.com/tutorial/floating_point/understanding_floating_point_representation.html
Note the section:
"III. Effective FP Programming"
...
"Equality"
"First let's tackle that pesky issue of equality: why is it so hard to know when
two floats are equal?"
Why Floating-Point Numbers May Lose Precision
https://msdn.microsoft.com/en-us/library/c151dt3s.aspx
- Wayne
reference:
https://www.geeksforgeeks.org/interesting-facts-about-switch-statement-in-c/