[cfe-dev] Lookahead vs. Tentative Parsing

John McCall rjmccall at apple.com
Tue Jul 5 21:33:12 PDT 2011


On Jul 5, 2011, at 9:22 PM, David Blaikie wrote:

> Since C++ lambda expressions and Objective-C message expressions can
> each start with the same two tokens (l_square followed by identifier),
> it can take a lookahead of three tokens to differentiate the two cases.
> 
> I'm playing around with implementing this myself. But why would you need a lookahead when these only appear in distinct languages? Currently there's a "if objective C, start parsing a message" I was just going to add an "if C++, start parsing a lambda" after that.

Objective-C++ exists and is important to a lot of our developers;  any implementation of lambdas in Clang will eventually need to handle both.

John.
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