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ccomma-operator

C Standard - Comma Operator Syntax

according to the C Standard (and K&R) the syntax of the Comma-Operator is as follows:

expression:
    assignment-expression
    expression, assignment-expression

But why does this statement work?

5+5, 1+1;

5+5 and 1+1 are not assignment-expressions, but the C Standard requires assignment-expressions as operands for the Comma-Operator.

Solution

  • assignment-expression ⊃ conditional-expression ⊃ logical-OR-expression ⊃ logical-AND-expression ⊃ inclusive-OR-expression ⊃ exclusive-OR-expression ⊃ AND-expression ⊃ equality-expression ⊃ relational-expression ⊃ shift-expression ⊃ additive-expression which finally are ⊃ additive-expression + multiplicative-expression.

    So no, 5+5 is indeed ∈ assignment-expression.

    ⊃ is the "contains" relation.