C language (as well as C++) is historically a mix of two completely different programming styles, which one can refer to as “statement programming” and “expression programming”. As you know, every procedural programming language normally supports such fundamental constructs as sequencing and branching (see Structured Programming). These fundamental constructs are present in C/C++ languages in … Read more
The comma operator evaluates both of its operands (from left to right) and returns the value of the second operand. Source: https://developer.mozilla.org/en/JavaScript/Reference/Operators/Special_Operators/Comma_Operator For example, the expression 1,2,3,4,5 evaluates to 5. Obviously the comma operator is useful only for operations with side-effects. console.log(1,2,3,4,5); console.log((1,2,3,4,5));
A common idiom is to use the comma operator which evaluates both operands, and returns the second operand. Thus: for(int i = 0; i != 5; ++i,++j) do_something(i,j); But is it really a comma operator? Now having wrote that, a commenter suggested it was actually some special syntactic sugar in the for statement, and not … Read more
The following is probably not very useful as you don’t write it yourself, but a minifier can shrink code using the comma operator. For example: if(x){foo();return bar()}else{return 1} would become: return x?(foo(),bar()):1 The ? : operator can be used now, since the comma operator (to a certain extent) allows for two statements to be written … Read more
In the expression (i, ++i, 1), the comma used is the comma operator the comma operator (represented by the token ,) is a binary operator that evaluates its first operand and discards the result, and then evaluates the second operand and returns this value (and type). Because it discards its first operand, it is generally … Read more
Take care to notice that the comma operator may be overloaded in C++. The actual behaviour may thus be very different from the one expected. As an example, Boost.Spirit uses the comma operator quite cleverly to implement list initializers for symbol tables. Thus, it makes the following syntax possible and meaningful: keywords = “and”, “or”, … Read more
The expression: (expression1, expression2) First expression1 is evaluated, then expression2 is evaluated, and the value of expression2 is returned for the whole expression.