Switch

[Georg Wrede]

Andrei Alexandrescu wrote:
> Georg Wrede wrote:
>> bearophile wrote:
>>>
>>> void classify(char c) {
>>>     write("You passed ");
>>>     switch (c) {
>>>        case '#':
>>>           writeln("a hash sign.");
>>>           break;
>>>        case '0' ..> '9':
>>>           writeln("a digit.");
>>>           break;
>>>        case 'A' ..> 'Z', 'a' ..> 'z':
>>>           writeln("an ASCII character.");
>>>           break;
>>>        case '.', ',', ':', ';', '!', '?':
>>>           writeln("a punctuation mark.");
>>>           break;
>>>        default:
>>>           writeln("quite a character!");
>>>           break;
>>>     }
>>> }
>> (A bunch of other versions omitted.)...
>>
>>
>>  void classify(char c) {
>>      write("You passed ");
>>      switch (c) {
>>         case '#':
>>            writeln("a hash sign.");
>>            break;
>>         case '0' .. case '9':
>>            writeln("a digit.");
>>            break;
>>         case 'A' .. case 'Z':
>>         case 'a' .. case 'z':
>>            writeln("an ASCII character.");
>>            break;
>>         case '.', ',', ':', ';', '!', '?':
>>            writeln("a punctuation mark.");
>>            break;
>>         default:
>>            writeln("quite a character!");
>>            break;
>>      }
>>  }
>>
>> This is usable, easy to read -- and the programmer has no problem to 
>> remember that .. works differently in case statements than in ranges.
> 
> I'd like to keep the (non-required) colon after the first expression in 
> a ".." pair of case labels, that is:
> 
> case '0': .. case '9':
> 
> as opposed to
> 
> case '0' .. case '9':
> 
> That way it is abundantly clear that the notation has nothing in common 
> with expression1 .. expression2. The error message if someone forgot the 
> ':' can easily be made clear.

So concatenating ranges would be

     case '0': .. case '9': case 'a': .. case 'z':
         do something

which then could be written, depending on programmer preferences

     case '0':
     .. case '9':
     case 'a':
     .. case 'z':
         do something

or

     case '0': .. case '9':
     case 'a': .. case 'z':
         do something

While I'd prefer to omit the colon, I can live with it.