Subject: Re: [boost] Is there interest in a library for string-convertible enums?
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2014-10-28 19:57:00
On 29/10/2014 00:09, Felix Uhl wrote:
> So far, the only way to convert an enumeration value to a string is
> a lot of boilerplate code consisting of switch case statements for
> every single possible value of the enum.
Not the only way. The method I use is to create a lookup table via a
little macro magic. Granted that I'm then doing a linear scan through
the table (whereas a switch statement could be more efficient, or
knowledge that the enum is contiguous and could therefore do an index
lookup), but having a table allows for other useful queries, and I
wanted something that could be defined statically.
As a side-benefit (that undoubtedly will horrify some people), the way
the code was implemented also allows it to act as a
string-to-member-pointer lookup table, which can be quite handy for
typed property bags and the like with a string lookup key.
> What features would you want from such a library?
Features that I would expect of such a library:
- support for arbitrary non-contiguous values.
- enum value to string.
- string to enum value.
- list of all valid values, either as strings or values.
- can indicate whether a given value (string or enum) is a member of
the enumeration.
- can round-trip (enum -> string -> enum) values that are not members
of the enumeration; of course (string -> enum -> string) is not feasible
for non-members.
- can specify a custom string value that the enum value generates (not
just the BOOST_PP_STRINGIZE).
Features that would be nice, but not necessarily expected:
- enum to string and back for "bitwise flag" style enums (eg. CSV names).
- some mapping to std::bitset or similar.
- can specify multiple string values that map to the same enum value.
- can specify different conversion tables for the same enum type (for
use in different contexts, eg. serialisation vs. user output).