[preprocessor] Identity function for token concatenation
Boost.Preprocessor has a macro BOOST_PP_INTERCEPT to eat a numeric value that it is token-concatenated onto. Is there a similar macro that just returns the value? I.e., some BOOST_PP_EMPTY_FOR_CONCAT such that BOOST_PP_EMPTY_FOR_CONCAT ## 3 turns into 3? As with BOOST_PP_INTERCEPT, it only needs to work for small integer values. Is there some other technique I can use for this? I am using it to generate std::get<> invocations in BOOST_PP_ENUM_BINARY_PARAMS. Thank you for your help. -- Jeremiah Willcock
On Mon, Jun 18, 2012 at 10:35 AM, Jeremiah Willcock <jewillco@osl.iu.edu>wrote:
Boost.Preprocessor has a macro BOOST_PP_INTERCEPT to eat a numeric value that it is token-concatenated onto. Is there a similar macro that just returns the value? I.e., some BOOST_PP_EMPTY_FOR_CONCAT such that BOOST_PP_EMPTY_FOR_CONCAT ## 3 turns into 3? As with BOOST_PP_INTERCEPT, it only needs to work for small integer values. Is there some other technique I can use for this? I am using it to generate std::get<> invocations in BOOST_PP_ENUM_BINARY_PARAMS. Thank you for your help.
I don't know any such facility in Boost.PP, but it's pretty trivial to generate: #define X0 0 #define X1 1 #define X2 2 // etc. ...which makes me think I might be overlooking something in Boost.PP :/ Somewhat related: what do your ENUM_BINARY_PARAMS invocations look like? I know I've gotten away with cat'ing template parameter delimiters ("<" and ">") against preprocessor integer tokens. Probably not really helping, - Jeff
On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 10:35 AM, Jeremiah Willcock <jewillco@osl.iu.edu> wrote: Boost.Preprocessor has a macro BOOST_PP_INTERCEPT to eat a numeric value that it is token-concatenated onto. Is there a similar macro that just returns the value? I.e., some BOOST_PP_EMPTY_FOR_CONCAT such that BOOST_PP_EMPTY_FOR_CONCAT ## 3 turns into 3? As with BOOST_PP_INTERCEPT, it only needs to work for small integer values. Is there some other technique I can use for this? I am using it to generate std::get<> invocations in BOOST_PP_ENUM_BINARY_PARAMS. Thank you for your help.
I don't know any such facility in Boost.PP, but it's pretty trivial to generate:
#define X0 0 #define X1 1 #define X2 2 // etc.
...which makes me think I might be overlooking something in Boost.PP :/
Somewhat related: what do your ENUM_BINARY_PARAMS invocations look like? I know I've gotten away with cat'ing template parameter delimiters ("<" and ">") against preprocessor integer tokens.
I'm not using this code anymore, but it was basically: BOOST_PP_ENUM_BINARY_PARAMS(nparams, std::get<ZZZ, >(tup) BOOST_PP_INTERCEPT) where ZZZ is the identity-type macro discussed in the email. Even using something that I would expect to work like + as ZZZ breaks since apparently signs aren't allowed at the beginnings of pp-tokens. I'm using GCC 4.7, and it seems to be strict about concatenations. -- Jeremiah Willcock
On Mon, Jun 18, 2012 at 12:25 PM, Jeremiah Willcock <jewillco@osl.iu.edu>wrote:
On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 10:35 AM, Jeremiah Willcock <jewillco@osl.iu.edu>
wrote: Boost.Preprocessor has a macro BOOST_PP_INTERCEPT to eat a numeric value that it is token-concatenated onto. Is there a similar macro that just returns the value? I.e., some BOOST_PP_EMPTY_FOR_CONCAT such that BOOST_PP_EMPTY_FOR_CONCAT ## 3 turns into 3? As with BOOST_PP_INTERCEPT, it only needs to work for small integer values. Is there some other technique I can use for this? I am using it to generate std::get<> invocations in BOOST_PP_ENUM_BINARY_PARAMS. Thank you for your help.
I don't know any such facility in Boost.PP, but it's pretty trivial to generate:
#define X0 0 #define X1 1 #define X2 2 // etc.
...which makes me think I might be overlooking something in Boost.PP :/
Somewhat related: what do your ENUM_BINARY_PARAMS invocations look like? I know I've gotten away with cat'ing template parameter delimiters ("<" and ">") against preprocessor integer tokens.
I'm not using this code anymore, but it was basically:
BOOST_PP_ENUM_BINARY_PARAMS(**nparams, std::get<ZZZ, >(tup) BOOST_PP_INTERCEPT)
where ZZZ is the identity-type macro discussed in the email. Even using something that I would expect to work like + as ZZZ breaks since apparently signs aren't allowed at the beginnings of pp-tokens. I'm using GCC 4.7, and it seems to be strict about concatenations.
So, just to confirm, BOOST_PP_ENUM_BINARY_PARAMS( nparams, std::get<, >(tup) BOOST_PP_INTERCEPT ) (i.e., with ZZZ being an empty token) does not work with gcc 4.7? - Jeff
On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 12:25 PM, Jeremiah Willcock <jewillco@osl.iu.edu> wrote: On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 10:35 AM, Jeremiah Willcock <jewillco@osl.iu.edu> wrote: Boost.Preprocessor has a macro BOOST_PP_INTERCEPT to eat a numeric value that it is token-concatenated onto. Is there a similar macro that just returns the value? I.e., some BOOST_PP_EMPTY_FOR_CONCAT such that BOOST_PP_EMPTY_FOR_CONCAT ## 3 turns into 3? As with BOOST_PP_INTERCEPT, it only needs to work for small integer values. Is there some other technique I can use for this? I am using it to generate std::get<> invocations in BOOST_PP_ENUM_BINARY_PARAMS. Thank you for your help.
I don't know any such facility in Boost.PP, but it's pretty trivial to generate:
#define X0 0 #define X1 1 #define X2 2 // etc.
...which makes me think I might be overlooking something in Boost.PP :/
Somewhat related: what do your ENUM_BINARY_PARAMS invocations look like? I know I've gotten away with cat'ing template parameter delimiters ("<" and ">") against preprocessor integer tokens.
I'm not using this code anymore, but it was basically:
BOOST_PP_ENUM_BINARY_PARAMS(nparams, std::get<ZZZ, >(tup) BOOST_PP_INTERCEPT)
where ZZZ is the identity-type macro discussed in the email. Even using something that I would expect to work like + as ZZZ breaks since apparently signs aren't allowed at the beginnings of pp-tokens. I'm using GCC 4.7, and it seems to be strict about concatenations.
So, just to confirm,
BOOST_PP_ENUM_BINARY_PARAMS( nparams, std::get<, >(tup) BOOST_PP_INTERCEPT )
(i.e., with ZZZ being an empty token) does not work with gcc 4.7?
Unless "empty token" means something other than putting nothing there, it expands to what I want but produces errors: foo.cpp:3:1: error: pasting "<" and "0" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "1" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "2" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "3" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "4" does not give a valid preprocessing token std::get< 0 >(tup) , std::get< 1 >(tup) , std::get< 2 >(tup) , std::get< 3 >(tup) , std::get< 4 >(tup) When trying to expand: BOOST_PP_ENUM_BINARY_PARAMS(5, std::get<, >(tup) BOOST_PP_INTERCEPT) -- Jeremiah Willcock
On Mon, Jun 18, 2012 at 12:34 PM, Jeremiah Willcock <jewillco@osl.iu.edu>wrote:
On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 12:25 PM, Jeremiah Willcock <jewillco@osl.iu.edu>
wrote: On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 10:35 AM, Jeremiah Willcock < jewillco@osl.iu.edu> wrote: Boost.Preprocessor has a macro BOOST_PP_INTERCEPT to eat a numeric value that it is token-concatenated onto. Is there a similar macro that just returns the value? I.e., some BOOST_PP_EMPTY_FOR_CONCAT such that BOOST_PP_EMPTY_FOR_CONCAT ## 3 turns into 3? As with BOOST_PP_INTERCEPT, it only needs to work for small integer values. Is there some other technique I can use for this? I am using it to generate std::get<> invocations in BOOST_PP_ENUM_BINARY_PARAMS. Thank you for your help.
I don't know any such facility in Boost.PP, but it's pretty trivial to generate:
#define X0 0 #define X1 1 #define X2 2 // etc.
...which makes me think I might be overlooking something in Boost.PP :/
Somewhat related: what do your ENUM_BINARY_PARAMS invocations look like? I know I've gotten away with cat'ing template parameter delimiters ("<" and ">") against preprocessor integer tokens.
I'm not using this code anymore, but it was basically:
BOOST_PP_ENUM_BINARY_PARAMS(**nparams, std::get<ZZZ, >(tup) BOOST_PP_INTERCEPT)
where ZZZ is the identity-type macro discussed in the email. Even using something that I would expect to work like + as ZZZ breaks since apparently signs aren't allowed at the beginnings of pp-tokens. I'm using GCC 4.7, and it seems to be strict about concatenations.
So, just to confirm,
BOOST_PP_ENUM_BINARY_PARAMS( nparams, std::get<, >(tup) BOOST_PP_INTERCEPT )
(i.e., with ZZZ being an empty token) does not work with gcc 4.7?
Unless "empty token" means something other than putting nothing there, it expands to what I want but produces errors:
foo.cpp:3:1: error: pasting "<" and "0" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "1" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "2" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "3" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "4" does not give a valid preprocessing token std::get< 0 >(tup) , std::get< 1 >(tup) , std::get< 2 >(tup) , std::get< 3 >(tup) , std::get< 4 >(tup)
When trying to expand:
BOOST_PP_ENUM_BINARY_PARAMS(5, std::get<, >(tup) BOOST_PP_INTERCEPT)
Sounds like I might need to change my preprocessor programming habits :( How about using a leading 0? BOOST_PP_ENUM_BINARY_PARAMS( nparams, std::get< 0, >(tup) BOOST_PP_INTERCEPT ) - Jeff
On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 12:34 PM, Jeremiah Willcock <jewillco@osl.iu.edu> wrote: On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 12:25 PM, Jeremiah Willcock <jewillco@osl.iu.edu> wrote: On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 10:35 AM, Jeremiah Willcock <jewillco@osl.iu.edu> wrote: Boost.Preprocessor has a macro BOOST_PP_INTERCEPT to eat a numeric value that it is token-concatenated onto. Is there a similar macro that just returns the value? I.e., some BOOST_PP_EMPTY_FOR_CONCAT such that BOOST_PP_EMPTY_FOR_CONCAT ## 3 turns into 3? As with BOOST_PP_INTERCEPT, it only needs to work for small integer values. Is there some other technique I can use for this? I am using it to generate std::get<> invocations in BOOST_PP_ENUM_BINARY_PARAMS. Thank you for your help.
I don't know any such facility in Boost.PP, but it's pretty trivial to generate:
#define X0 0 #define X1 1 #define X2 2 // etc.
...which makes me think I might be overlooking something in Boost.PP :/
Somewhat related: what do your ENUM_BINARY_PARAMS invocations look like? I know I've gotten away with cat'ing template parameter delimiters ("<" and ">") against preprocessor integer tokens.
I'm not using this code anymore, but it was basically:
BOOST_PP_ENUM_BINARY_PARAMS(nparams, std::get<ZZZ, >(tup) BOOST_PP_INTERCEPT)
where ZZZ is the identity-type macro discussed in the email. Even using something that I would expect to work like + as ZZZ breaks since apparently signs aren't allowed at the beginnings of pp-tokens. I'm using GCC 4.7, and it seems to be strict about concatenations.
So, just to confirm,
BOOST_PP_ENUM_BINARY_PARAMS( nparams, std::get<, >(tup) BOOST_PP_INTERCEPT )
(i.e., with ZZZ being an empty token) does not work with gcc 4.7?
Unless "empty token" means something other than putting nothing there, it expands to what I want but produces errors:
foo.cpp:3:1: error: pasting "<" and "0" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "1" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "2" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "3" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "4" does not give a valid preprocessing token std::get< 0 >(tup) , std::get< 1 >(tup) , std::get< 2 >(tup) , std::get< 3 >(tup) , std::get< 4 >(tup)
When trying to expand:
BOOST_PP_ENUM_BINARY_PARAMS(5, std::get<, >(tup) BOOST_PP_INTERCEPT)
Sounds like I might need to change my preprocessor programming habits :(
How about using a leading 0?
BOOST_PP_ENUM_BINARY_PARAMS( nparams, std::get< 0, >(tup) BOOST_PP_INTERCEPT )
I was using numbers large enough that marking them as octal (or even hex) would break, so adding 0 or 0x won't work. I guess you could use: BOOST_PP_ENUM_BINARY_PARAMS(nparams, std::get<1000, %100>(tup) BOOST_PP_INTERCEPT) though. -- Jeremiah Willcock
On Mon, Jun 18, 2012 at 12:55 PM, Jeremiah Willcock <jewillco@osl.iu.edu>wrote:
On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 12:34 PM, Jeremiah Willcock <jewillco@osl.iu.edu>
wrote: On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 12:25 PM, Jeremiah Willcock < jewillco@osl.iu.edu> wrote: On Mon, 18 Jun 2012, Jeffrey Lee Hellrung, Jr. wrote:
On Mon, Jun 18, 2012 at 10:35 AM, Jeremiah Willcock <jewillco@osl.iu.edu> wrote: Boost.Preprocessor has a macro BOOST_PP_INTERCEPT to eat a numeric value that it is token-concatenated onto. Is there a similar macro that just returns the value? I.e., some BOOST_PP_EMPTY_FOR_CONCAT such that BOOST_PP_EMPTY_FOR_CONCAT ## 3 turns into 3? As with BOOST_PP_INTERCEPT, it only needs to work for small integer values. Is there some other technique I can use for this? I am using it to generate std::get<> invocations in BOOST_PP_ENUM_BINARY_PARAMS. Thank you for your help.
I don't know any such facility in Boost.PP, but it's pretty trivial to generate:
#define X0 0 #define X1 1 #define X2 2 // etc.
...which makes me think I might be overlooking something in Boost.PP :/
Somewhat related: what do your ENUM_BINARY_PARAMS invocations look like? I know I've gotten away with cat'ing template parameter delimiters ("<" and ">") against preprocessor integer tokens.
I'm not using this code anymore, but it was basically:
BOOST_PP_ENUM_BINARY_PARAMS(**nparams, std::get<ZZZ,
(tup) BOOST_PP_INTERCEPT)
where ZZZ is the identity-type macro discussed in the email. Even using something that I would expect to work like + as ZZZ breaks since apparently signs aren't allowed at the beginnings of pp-tokens. I'm using GCC 4.7, and it seems to be strict about concatenations.
So, just to confirm,
BOOST_PP_ENUM_BINARY_PARAMS( nparams, std::get<, >(tup) BOOST_PP_INTERCEPT )
(i.e., with ZZZ being an empty token) does not work with gcc 4.7?
Unless "empty token" means something other than putting nothing there, it expands to what I want but produces errors:
foo.cpp:3:1: error: pasting "<" and "0" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "1" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "2" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "3" does not give a valid preprocessing token foo.cpp:3:1: error: pasting "<" and "4" does not give a valid preprocessing token std::get< 0 >(tup) , std::get< 1 >(tup) , std::get< 2 >(tup) , std::get< 3 >(tup) , std::get< 4 >(tup)
When trying to expand:
BOOST_PP_ENUM_BINARY_PARAMS(5, std::get<, >(tup) BOOST_PP_INTERCEPT)
Sounds like I might need to change my preprocessor programming habits :(
How about using a leading 0?
BOOST_PP_ENUM_BINARY_PARAMS( nparams, std::get< 0, >(tup) BOOST_PP_INTERCEPT )
I was using numbers large enough that marking them as octal (or even hex) would break, so adding 0 or 0x won't work. I guess you could use:
BOOST_PP_ENUM_BINARY_PARAMS(**nparams, std::get<1000, %100>(tup) BOOST_PP_INTERCEPT)
though.
Well, I learned a new trick :) Probably your hypothetical BOOST_PP_IDENTITY_WHEN_CAT would be clearer (if not more verbose). - Jeff
On 06/18/2012 10:07 PM, Jeffrey Lee Hellrung, Jr. wrote:
Well, I learned a new trick
Probably your hypothetical BOOST_PP_IDENTITY_WHEN_CAT would be clearer (if not more verbose).
Why not usign BOOST_PP_ENUM with a custom enumerator #define M0(z,n,t) std::get<n>(t) BOOST_PP_ENUM( nparams, M0, tup ) ?
participants (1)
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Jeffrey Lee Hellrung, Jr. -
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Joel Falcou