Double closing angle brackets (>>) generate syntax error in SPECIFIC case

Question

Eclipse (Luna, 4.4.2) tells me that I have a syntax error on the following line:

static_cast>(a.mul(b));

I rememb

Answer 1

The "right angle bracket fix" is found in §14.2 [temp.names]/p3 (emphasis mine):

When parsing a template-argument-list, the first non-nested > is taken as the ending delimiter rather than a greater-than operator. Similarly, the first non-nested >> is treated as two consecutive but distinct > tokens, the first of which is taken as the end of the template-argument-list and completes the template-id. [ Note: The second > token produced by this replacement rule may terminate an enclosing template-id construct or it may be part of a different construct (e.g. a cast).—end note ]

If the static_cast is otherwise valid, then both pieces of code in the OP are perfectly valid in C++11 and perfectly invalid in C++03. If your IDE reports an error on one but not the other, then it's a bug with that IDE.

It's difficult (and also somewhat pointless) for us to speculate on the source of the bug. A potential cause can be that the second > are closing different constructs (the first case it's closing a cast, the second is closing a template argument list) and the parser's implementation somehow missed the "second > being part of a different construct" case. But that's just wild speculation.

Answer 2

You have used a pre c++11 standard compiler. The older standard had a problem letting the parser disambiguate a pair of closing angle brackets >> used in a nested template type specifier, from the operator>>(). Thus you had to write a space between them.

The samples like >>> or >>* are falling under a different case for the old parsers, thus they work without error message.

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_{I have to admit, I don't actually know what exactly was done in the c++11 (the current) standards definitions, that this situation can be clearly disambiguated by a c++11 compliant parser.}