From: Iain Denniston (iain.denniston_at_[hidden])
Date: 2007-08-14 05:42:36
[Uploaded to the vault (flags_v1.zip) complete with docs and test file
(no jam file yet sorry) - tested in vc8 and MinGW GCC 3.4.2.]
Ive proposed this before and gotten a little interest so I figured
Id try again (particularly now that 1.34.1 is out) and see if I could
get some more interest! At its most simple, its a way to stop function
users providing difficult to detect erroneous data. The best way to work
out what this lib does is probably read the docs I uploaded, but for
here Ill take one of the examples I use from the docs:
foo_1 = 1<<0,
foo_2 = 1<<1,
bar_1 = 1<<2,
bar_2 = 1<<3,
void func1(unsigned int options)
void func2(flags<foo> options)
int main(int argc, char * argv)
func1(foo_1 | foo_2 | bar_1 | bar_2); //Compiles fine
func2(flags<foo>(foo_1) | foo_2 | bar_1 | bar_2); //Compile time error
- cannot convert bar to foo
Additionally, sometimes it is useful to force the user to supply a flag
rather than allow them to supply none (i.e. '0') - the flags_no_default
provides this functionality.
The library is not very big and its not very clever :) but the hope is
to push errors back to compile time, at little or no runtime cost.
If people are interested or not either way its cool but since its
now in the vault anyone can use it if they want.
Hope it all makes sense! Questions/comments/criticism gratefully received.
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