3 ms·

The most vexing parse is not an issue in "C and C++ grammars", it is only an issue in C++ which has really stupid initialization syntax that looks like a functi

The most vexing parse is not an issue in "C and C++ grammars", it is only an issue in C++ which has really stupid initialization syntax that looks like a function call. C and C++ are not the same language nor even that similar. It's a shame they are always mentioned together under the same breath.

woodruffw 4y ago
Author here: the examples in the blog post are for C++, but a variant of the MVP also occurs in C when uniform declaration interacts with typedefs. Here's an old (1992!) comp.compilers post on it[1]. [1]: https://pdos.csail.mit.edu/archive/l/c/roskind.html https://pdos.csail.mit.edu/archive/l/c/roskind.html
- planede 4y ago
  I would say that these are context-sensitive, but it doesn't seem to be analogue to C++'s most vexing parse. In the most vexing parse case all identifiers are resolved to the correct kind (type name or variable name), yet it is still ambiguous. The C examples are unambiguous after the kind of the identifiers are identified. A C exmaple: T(*ptr)[42]; If T is a type then this is a declarations of a pointer to an array of T. If T is a function, then this is a function call followed by a subscript (which is then discarded). A similar C++ analogue would be: C<0>(0); If C is a function template with a non-type template parameter, then this is a function call of C<0> with argument 0. If C is an int variable instead then it is equivalent to the following expression (C < 0) > 0 . But for T a(); in both possible interpretations T is a type, and 'a' is the new entity being declared. So parsing this is not context-sensitive, it's simply ambiguous. C++ resolves the ambiguity by choosing in favor of function declarations. I'm not aware of a C analogue similar to this.
  - woodruffw 4y ago
    To be clear: I'm not claiming they're analogous, only that they're both consequences of uniform declaration and are historically grouped together when talking about "vexing parses."
pdmccormick 4y ago
If I ever see a resume or a job description that lists "C/C++", that's a red flag to me that either someone might not actually have that much experience, or someone doesn't actually know what they are looking for.
- woodruffw 4y ago
  IME, people who list "C/C++" on their resumes tend to be recent undergraduates. When asked about it, they usually have C experience from one or two systems courses, and C++ experience from a separate course. Undergraduate courses tend to teach C++ as an "extension" of C because it eliminates the hump (and anxiety) of teaching an entirely new language, at the cost of being technically misleading.
- pjmlp 4y ago
  You will find plenty of those from the job boards of the companies that seat at ISO C++, and their SDK documentation. Once upon a time, "The C/C++ Users' Journal" was the reference magazine for C and C++ developers. As per English grammar rules, / is an abbreviation, https://eslgrammar.org/forward-slash/ https://eslgrammar.org/forward-slash/

woodruffw 4y ago

Author here: the examples in the blog post are for C++, but a variant of the MVP also occurs in C when uniform declaration interacts with typedefs. Here's an old (1992!) comp.compilers post on it[1]. [1]: https://pdos.csail.mit.edu/archive/l/c/roskind.html https://pdos.csail.mit.edu/archive/l/c/roskind.html

planede 4y ago
I would say that these are context-sensitive, but it doesn't seem to be analogue to C++'s most vexing parse. In the most vexing parse case all identifiers are resolved to the correct kind (type name or variable name), yet it is still ambiguous. The C examples are unambiguous after the kind of the identifiers are identified. A C exmaple: T(*ptr)[42]; If T is a type then this is a declarations of a pointer to an array of T. If T is a function, then this is a function call followed by a subscript (which is then discarded). A similar C++ analogue would be: C<0>(0); If C is a function template with a non-type template parameter, then this is a function call of C<0> with argument 0. If C is an int variable instead then it is equivalent to the following expression (C < 0) > 0 . But for T a(); in both possible interpretations T is a type, and 'a' is the new entity being declared. So parsing this is not context-sensitive, it's simply ambiguous. C++ resolves the ambiguity by choosing in favor of function declarations. I'm not aware of a C analogue similar to this.
- woodruffw 4y ago
  To be clear: I'm not claiming they're analogous, only that they're both consequences of uniform declaration and are historically grouped together when talking about "vexing parses."

pdmccormick 4y ago

If I ever see a resume or a job description that lists "C/C++", that's a red flag to me that either someone might not actually have that much experience, or someone doesn't actually know what they are looking for.

woodruffw 4y ago
IME, people who list "C/C++" on their resumes tend to be recent undergraduates. When asked about it, they usually have C experience from one or two systems courses, and C++ experience from a separate course. Undergraduate courses tend to teach C++ as an "extension" of C because it eliminates the hump (and anxiety) of teaching an entirely new language, at the cost of being technically misleading.
pjmlp 4y ago
You will find plenty of those from the job boards of the companies that seat at ISO C++, and their SDK documentation. Once upon a time, "The C/C++ Users' Journal" was the reference magazine for C and C++ developers. As per English grammar rules, / is an abbreviation, https://eslgrammar.org/forward-slash/ https://eslgrammar.org/forward-slash/