From: Yohanes Santoso <ysantoso-rubytalk@...>
Date: 2005-08-03T01:58:28+09:00
Subject: Re: enum collection of constant values

Garance A Drosehn <drosihn@gmail.com> writes:

> I'd like to have a set of constants for a class, where their values
> need to be unique, and preferably compact.  For instance:
>    SB_NONE = 0; SB_GOOD = 1; SB_BAD = 2; SB_LOGIC_ERR = 3;
>    SB_MAX = SB_LOGIC_ERR
>
> but if I want to modify this list by adding something in the middle,
> then I have to remember to increment (by hand) all the values
> which come after that new value.
>
> In C, I would do something like:
>     typedef enum { SB_NONE, SB_GOOD, SB_BAD,
>         SB_LOGICERR } sb_set;

SB_ENUM = {:none => 0, :good => 1, :bad => 2, :logic_err => 4}.freeze
SB_MAX = SB_ENUM.values.max

value = SB_ENUM[:bad] | SB_ENUM[:logic_err]

p SB_ENUM[:invalid_enum_value] # ==> nil


YS.

>
> Looking through the pickaxe book, it looks like the closest thing
> I can do is to create an array of words, and then use the indexes
> of where those words are in the array.  But that isn't really the
> same thing.   I'd like the efficiency of having constant values,
> which would be referred to by name.
>
> (And after I have that for a compact set of values, I'd want a
> similar feature which would give me a bit-wise unique set of
> values.  Eg:  SB_MODA = 1; SB_MODB = 2; SB_MODC = 4;
> SB_MODD = 8; -- such that I could combine the values together
> using '|', and tell which values were 'or'-ed together to get that
> combined value...)
>
> -- 
> Garance Alistair Drosehn     =             drosihn@gmail.com
> Senior Systems Programmer               or   gad@FreeBSD.org
> Rensselaer Polytechnic Institute;             Troy, NY;  USA