Comma-Separated Expressions

Discussion in 'C' started by pradeep, May 22, 2006.

  1. pradeep

    pradeep Team Leader

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    Comma-separated expressions were inherited from C. It's likely that you use such expressions in for- and while-loops rather often. Yet, the language rules in this regard are far from being intuitive. First, let's see what a comma separated expression is.

    An expression may consist of one or more sub-expressions separated by commas. For example:
    Code:
     if(++x, --y, cin.isInt()) /*three expressions*/
    The if condition contains three expressions separated by commas. C++ ensures that each of the expressions is evaluated and its side effects take place. However, the value of an entire comma-separated expression is only the result of the rightmost expression. Therefore, the if condition above evaluates as true only if cin.isInt() returns true. Here's another example of a comma expression:

    Code:
    int j=10;
     int i=0;
     while( ++i, --j)
     {
     /*..repeat as long as j is not 0*/
     }
     
     
  2. Aztec

    Aztec New Member

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    Nice...Moderator should add this to Tips.
     
  3. shabbir

    shabbir Administrator Staff Member

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    Added.
     
  4. rahul.mca2001

    rahul.mca2001 New Member

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