Multiple character comparisons, how can I write it smarter?

Question

I am parsing a text-file. While parsing, I want to skip certain characters (space, line-break, comma, period). In PHP, one may check the existence of a variable in an array with in_array(char, array), but things are obviously different given we are working with pointers.

I am currently writing it like this (excuse the weird formatting)

if (c == ' '  || 
    c == '\n' || 
    c == '.'  || 
    c == ',') {

  continue;
}

But it feels a bit dumb. Is there a smarter/more compact way to perform multiple comparisons like this?

Hard to guess what's "dumb" about it. Maybe you ought to write a one-liner isPunctuation(char) function. Maybe you shouldn't [try too hard](http://stackoverflow.com/questions/26124620/why-does-msvc-emit-a-useless-movsx-before-performing-this-bit-test). — Hans Passant, Oct 27 '14 at 17:53

score 3 · Answer 1 · answered Oct 27 '14 at 17:49

3

Try this:

switch(c) {
  case ' ':
  case '\n':
  case '.:
  case ',':
    continue;
}

answered Oct 27 '14 at 17:49

Linuxios

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score 3 · Accepted Answer · answered Oct 27 '14 at 17:55

3

Another choice would be to use strchr to check if a given character is in a given string:

if (strchr(" \n.,", c)
    continue;

answered Oct 27 '14 at 17:55

Brian Campbell

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This is exactly what I was looking for. Thanks! – krystah Oct 27 '14 at 18:05
Note: `c` will match the 4 desired `char`: `' '`, `'\n'`, `'.'`, `','` and `'\0'`. – chux - Reinstate Monica Oct 27 '14 at 18:16
1

@krystah If if it's time critical, your solution may still be better than the strchr solution. – Jabberwocky Oct 27 '14 at 18:19

score 1 · Answer 3 · answered Oct 27 '14 at 17:49

Use a function and pass a string with your characters:

_Bool Check( char a , char* str )
{
    while( *str )
    { 
        if( *str == a )
        {
            return true ;
        }

        str++ ;
    }

return false ;
}

Check( c , ",.\n " ) ;

Multiple character comparisons, how can I write it smarter?

3 Answers3

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