Name Recipes/Common/WordCount/CountInLine2

Synopsis Count words in a line.

Examples A slighly more involved manner of using regular matching in a loop.

module demo::common::WordCount::CountInLine2

public int countInLine2(str S){
  int count = 0;
  
  // \w matches any word character
  // \W matches any non-word character
  // <...> are groups and should appear at the top level.
  while (/^\W*<word:\w+><rest:.*$>/ := S) { 
    count += 1; 
    S = rest; 
  }
  return count;
}

The pattern /^\W*<word:\w+><rest:.*$>/ can be understood as follows:

• The ^ makes it anchored, only matches at the begin of the substring S.
• \W* matches zero or more non-word characters.
• <word:\w+> matches one or more word characters and assigns the result to the variable word.
• <rest:.*$> matches the remaining part of S.

Inside the loop count is incremented and the new value of S becomes the remainder of the current match. To summarize: each iteration removes the first word from S and counts it.

Here is `countInLine2 in action:

rascal>import demo::common::WordCount::CountInLine2;
ok
rascal>countInLine2("Jabberwocky by Lewis Carroll");
int: 4

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