Convert double to long if lossless

[Steven Schveighoffer]

On 1/19/21 6:42 AM, Per Nordlöw wrote:
> I want to convert a double to a long if conversion is lossless (without 
> fractional part, non-nan, non-inf, within long-range, etc).
> 
> I currently have
> 
> void foo()
> {
>      const double value = 10.1;
>      try
>      {
>          import std.conv : to;
>          const lvalue = value.to!long;
>          if (lvalue == value)
>          {
>              writeln("lvalue:", lvalue);
>              return;
>          }
>      }
>      catch (Exception e) {}
>      writeln("value:", value);
> }
> 
> Can this be improved?
> 
> For instance how do I check if a float/double/real has a fractional part 
> and avoid entering try-catch for those cases?

Use a cast instead.

const lvalue = cast(long)value;

-Steve