Larger than and less than in C switch statement

Question

I\'m trying to write a code that has a lot of comparison

Write a program in “QUANT.C” which “quantifies” numbers. Read an integer “x” and test it, pro

Answer 1

Why do you have a preference to use switch?

I'm asking because this sounds awfully like a 'homework question'. A compiler should deal with if/else construct just as efficiently as a switch (even if you weren't dealing with ranges).

Switch can't handle ranges as you have shown, but you could find a way to include switch by categorising the input first (using if/else) then using a switch statement to output the answer.

Answer 2

use type parameter pattern along with when clause e.g.

switch(a)
    {
        case * when (a>1000):
            printf("hugely positive");
            break;
        case * when (a>=100 && a<999):
            printf("very positive");
            break;
        case * when (a>=0 && a<100):
            printf("positive");
            break; }

Answer 3

(a>1000) evaluates to either 1 [true] or 0 [false].

Compile and you will get the error:

test_15.c:12: error: case label does not reduce to an integer constant

This means, you have to use an integer constant value for the case labels. An If-else if-else loop should work just fine for this case.

Answer 4

If you are using gcc, you have "luck" because it supports exactly what you want by using a language extension:

#include <limits.h>
...

switch(a)
{
case 1000 ... INT_MAX: // note: cannot omit the space between 1000 and ...
    printf("hugely positive");
   break;
case 100 ... 999:
    printf("very positive");
   break;
...
}

This is non-standard though, and other compilers will not understand your code. It's often mentioned that you should write your programs only using standard features ("portability").

So consider using the "streamlined" if-elseif-else construct:

if (a >= 1000)
{
    printf("hugely positive");
}
else if (a >= 100)
{
    printf("very positive");
}
else if ...
...
else // might put a helpful comment here, like "a <= -1000"
{
    printf("hugely negative");
}

Answer 5

Use:

switch (option(a)) {
    case (0): ...
    case (1): ...
    case (2): ...
    case (n): ...

Where the option() function is simply a function with if else.

It lets you keep the clean look of a switch and the logic part is elsewhere.

Answer 6

There is no clean way to solve this with switch, as cases need to be integral types. Have a look at if-else if-else.