Language: C++

#include <iostream>
#include <string>

#define LIGHT_FLY	48.00
#define FLY		 	51.00
#define BANTAM		54.00
#define FEATHER		57.00
#define LIGHT		60.00
#define LIGHT_WELTER 64.00
#define WELTER		69.00
#define LIGHT_MIDDLE 75.00
#define MIDDLE		81.00
#define LIGHT_HEAVY	91.00

using namespace std;

int main() {
	double weight;
	string strWeight;
	while(cin>>weight, !cin.eof()){
		strWeight = "";
		switch((int)weight){
			case LIGHT_FLY:
				strWeight = "light fly"; break;
			case FLY:
				strWeight = "fly"; break;
			case BANTAM:
				strWeight = "bantam"; break;
			case FEATHER:
				strWeight = "feather"; break;
			case LIGHT:
				strWeight = "light"; break;
			case LIGHT_WELTER:
				strWeight = "light welter"; break;
			case WELTER:
				strWeight = "welter"; break;
			case LIGHT_MIDDLE:
				strWeight = "light middle"; break;
			case MIDDLE:
				strWeight = "middle"; break;
			case LIGHT_HEAVY:
				strWeight = "light heavy"; break;
			default:
				strWeight = "heavy"; break;
		}
		cout<<strWeight<<endl;
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:25: error: conversion from 'double' to 'int' in a converted constant expression
    4 | #define LIGHT_FLY       48.00
      |                         ^~~~~
a.cc:23:30: note: in expansion of macro 'LIGHT_FLY'
   23 |                         case LIGHT_FLY:
      |                              ^~~~~~~~~
a.cc:4:25: error: could not convert '4.8e+1' from 'double' to 'int'
    4 | #define LIGHT_FLY       48.00
      |                         ^~~~~
      |                         |
      |                         double
a.cc:23:30: note: in expansion of macro 'LIGHT_FLY'
   23 |                         case LIGHT_FLY:
      |                              ^~~~~~~~~
a.cc:5:33: error: conversion from 'double' to 'int' in a converted constant expression
    5 | #define FLY                     51.00
      |                                 ^~~~~
a.cc:25:30: note: in expansion of macro 'FLY'
   25 |                         case FLY:
      |                              ^~~
a.cc:5:33: error: could not convert '5.1e+1' from 'double' to 'int'
    5 | #define FLY                     51.00
      |                                 ^~~~~
      |                                 |
      |                                 double
a.cc:25:30: note: in expansion of macro 'FLY'
   25 |                         case FLY:
      |                              ^~~
a.cc:6:25: error: conversion from 'double' to 'int' in a converted constant expression
    6 | #define BANTAM          54.00
      |                         ^~~~~
a.cc:27:30: note: in expansion of macro 'BANTAM'
   27 |                         case BANTAM:
      |                              ^~~~~~
a.cc:6:25: error: could not convert '5.4e+1' from 'double' to 'int'
    6 | #define BANTAM          54.00
      |                         ^~~~~
      |                         |
      |                         double
a.cc:27:30: note: in expansion of macro 'BANTAM'
   27 |                         case BANTAM:
      |                              ^~~~~~
a.cc:7:25: error: conversion from 'double' to 'int' in a converted constant expression
    7 | #define FEATHER         57.00
      |                         ^~~~~
a.cc:29:30: note: in expansion of macro 'FEATHER'
   29 |                         case FEATHER:
      |                              ^~~~~~~
a.cc:7:25: error: could not convert '5.7e+1' from 'double' to 'int'
    7 | #define FEATHER         57.00
      |                         ^~~~~
      |                         |
      |                         double
a.cc:29:30: note: in expansion of macro 'FEATHER'
   29 |                         case FEATHER:
      |                              ^~~~~~~
a.cc:8:25: error: conversion from 'double' to 'int' in a converted constant expression
    8 | #define LIGHT           60.00
      |                         ^~~~~
a.cc:31:30: note: in expansion of macro 'LIGHT'
   31 |                         case LIGHT:
      |                              ^~~~~
a.cc:8:25: error: could not convert '6.0e+1' from 'double' to 'int'
    8 | #define LIGHT           60.00
      |                         ^~~~~
      |                         |
      |                         double
a.cc:31:30: note: in expansion of macro 'LIGHT'
   31 |                         case LIGHT:
      |                              ^~~~~
a.cc:9:22: error: conversion from 'double' to 'int' in a converted constant expression
    9 | #define LIGHT_WELTER 64.00
      |                      ^~~~~
a.cc:33:30: note: in expansion of macro 'LIGHT_WELTER'
   33 |                         case LIGHT_WELTER:
      |                              ^~~~~~~~~~~~
a.cc:9:22: error: could not convert '6.4e+1' from 'double' to 'int'
    9 | #define LIGHT_WELTER 64.00
      |                      ^~~~~
      |                      |
      |                      double
a.cc:33:30: note: in expansion of macro 'LIGHT_WELTER'
   33 |                         case LIGHT_WELTER:
      |                              ^~~~~~~~~~~~
a.cc:10:25: error: conversion from 'double' to 'int' in a converted constant expression
   10 | #define WELTER          69.00
      |                         ^~~~~
a.cc:35:30: note: in expansion of macro 'WELTER'
   35 |                         case WELTER:
      |                              ^~~~~~
a.cc:10:25: error: could not convert '6.9e+1' from 'double' to 'int'
   10 | #define WELTER          69.00
      |                         ^~~~~
      |                         |
      |                         double
a.cc:35:30: note: in expansion of macro 'WELTER'
   35 |                         case WELTER:
      |                              ^~~~~~
a.cc:11:22: error: conversion from 'double' to 'int' in a converted constant expression
   11 | #define LIGHT_MIDDLE 75.00
      |                      ^~~~~
a.cc:37:30: note: in expansion of macro 'LIGHT_MIDDLE'
   37 |                         case LIGHT_MIDDLE:
      |                              ^~~~~~~~~~~~
a.cc:11:22: error: could not convert '7.5e+1' from 'double' to 'int'
   11 | #define LIGHT_MIDDLE 75.00
      |                      ^~~~~
      |                      |
      |                      double
a.cc:37:30: note: in expansion of macro 'LIGHT_MIDDLE'
   37 |                         case LIGHT_MIDDLE:
      |                              ^~~~~~~~~~~~
a.cc:12:25: error: conversion from 'double' to 'int' in a converted constant expression
   12 | #define MIDDLE          81.00
      |                         ^~~~~
a.cc:39:30: note: in expansion of macro 'MIDDLE'
   39 |                         case MIDDLE:
      |                              ^~~~~~
a.cc:12:25: error: could not convert '8.1e+1' from 'double' to 'int'
   12 | #define MIDDLE          81.00
      |                         ^~~~~
      |                         |
      |                         double
a.cc:39:30: note: in expansion of macro 'MIDDLE'
   39 |                         case MIDDLE:
      |                              ^~~~~~
a.cc:13:25: error: conversion from 'double' to 'int' in a converted constant expression
   13 | #define LIGHT_HEAVY     91.00
      |                         ^~~~~
a.cc:41:30: note: in expansion of macro 'LIGHT_HEAVY'
   41 |                         case LIGHT_HEAVY:
      |                              ^~~~~~~~~~~
a.cc:13:25: error: could not convert '9.1e+1' from 'double' to 'int'
   13 | #define LIGHT_HEAVY     91.00
      |                         ^~~~~
      |                         |
      |                         double
a.cc:41:30: note: in expansion of macro 'LIGHT_HEAVY'
   41 |                         case LIGHT_HEAVY:
      |                              ^~~~~~~~~~~