Re: [lmi] Why not DBL_MAX?

[Evgeniy Tarassov]

On 3/24/07, Greg Chicares <address@hidden> wrote:
> 20070316T1310Z_DBL_MAX_to_static_limit_maximum.patch
[...]
> makes good sense. But why use this:
>     double stratified_entity::limit_maximum = DBL_MAX;
> instead of just writing DBL_MAX?

Only to simplify the code. So that the same constant is named the same
way everywhere it is used. And of course only where it has the same
semantics.

> Is there some arcane reason, e.g., that this quantity:
>     static double const max_double = std::numeric_limits<double>::max();
> in a removed line might not equal DBL_MAX for some woeful
> compiler? (Really old versions of MinGW gcc did have an
> incorrect value for DBL_EPSILON.)

I don't know, but using the same value (DBL_MAX or
stratified_entity::limit_maximum), it ensures that the program will
not produce bogus output for such a compiler.

> Is the reason that the value might change someday? If so,
> why? So that we could make the algorithms that use it
> correct even for infinity? Or so that we could restrict
> them to "plausible" values, recognizing that we're really
> operating on currency and no one has even 1e37 dollars?

Two reasons for me to introduce such a constant was:
1) to make understanding and grepping the source code easier. If
additionally we introduce another static double in 'sigfpe.cpp' then
by grepping 'limit_maximum' one will only find occurences of this
constant for cases where it is used for stratified_entity limit array
values 'terminator'. When one sees DBL_MAX it only says the exact
value, not the real meaning of the constant in the local context.
2) to get rid of the repeating line
#include <cfloat> // DBL_MAX

--
With best wishes,
Evgeniy Tarassov