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The comma (,) operator

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• The comma operator
  • C (and Java) has a comma operator that can glue multiple expressions into one single expression

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  • Syntax:

    expr1 , expr2 , ... , exprN

    Meaning:

    Treat these N expressions expr1 , expr2 , ... , exprN syntactically as one expression Recall that an expression will always evaluate to a value The value of: expr1 , expr2 , ... , exprN is equal to the value of the last expression exprN.

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• Common usage of the comma operator
  • The most common usage of the comma operator is in the for-statement where you need to initialize multiple variables

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  • Example:

    Copy the 10 array elements A[0], A[1], ..., A[9] of array A into the array elements B[10], B[11], ..., B[19]

    Solution:

    for ( i = 0, j = 10; i < 10; i++, j++ ) B[j] = A[i];