One pretty important use for me is in writing clear for loops that use multiple counter variables. For example, suppose you have a loop like this: for((0 => int i), (0 => int j); i < max_value; i++, 2 +=> j) { // do stuff } Without this way of using the comma, the loop must be written like so: 0 => int j; for(0 => int i; i < max_value; i++) { // do stuff 2 +=> j; } Okay, thats fine, and often functionally equivalent, but its less maintainable. For example, you can't use the continue keyword in the loop, unless you also add the j += 2; part each time you continue. Also, you can't really tell how the loop iterates just by looking at the first line. In the comma-enabled version, its easy to see that this loop iterates i by 1 up to max_value, and j by 2 up to max_value * 2. In the second version, you need to look at the end of the loop block in addition to any continue statements to see how the loop iterates--who cares for simple loops, but nasty with crazy nesting loops. spencer Quoting Kassen :

2008/6/28 Jukka Akkanen :

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This seems to be similar to the comma operator in C, which lets you use multiple comma-separated sub-expressions in a context where only a single expression is allowed. An expression using the comma operator evaluates to the value of the last sub-expression. Note that the comma operator is very different from how && works.

Got it.

How and where is this useful?

Thanks!

Kas.