Re: [boost] Fixed-Point Decimal Interface

From: John Max Skaller (skaller_at_[hidden])
Date: 2001-05-19 19:13:28

Bill Seymour wrote:
> 
> I've been thinking about some of the points that Skaller
> and others brought up.  How's this?
> 
> - I agree that functions such as abs() should be friends,
>   not members.  I'm concerned, though, that some compilers
>   can't handle template friends. 

        I suppose it depends on the target audience.
If the class is intended for ISO Standardisation, the faults
of compilers not supporting the Standard should be disregarded:
the committee won't listen to such an argument.

> - I see Skaller's point about the two-argument ctor being
>   confusing.  At first I thought about suggesting to users
>   that they think of the comma as a decimal point; but then
>   I caught myself writing an octal constant. 8-)  I think
>   I've found a use for this ctor, though:
> 
>     numeric_limits< decimal<Scale> >::epsilon();
> 
>   returns decimal<Scale>(0, 1).  I suggest making this ctor
>   one of the "public implementation details" mentioned above.

        This suggests retaining the constructor, but making
it private, since the use seems limited <g>.
 
> - I still think that users ought to be able to mix decimals
>   of different scale factors in expressions.  

        I cannot say this is wrong. However, I have USED systems
that did that, mainly PL/1, and figuring out what is happening
is very hard.

        I suggest you implement mixed scale arithmetic
and try to use it to see what I mean.

> I suggest that
>   the result type always be the type of the left-hand argument.

        That is not symmetric. People expect symmetric
operators like addition to be symmetric:

        a + b == b + a

-- 
John (Max) Skaller, mailto:skaller_at_[hidden]
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