• Daniele M. (15/15) Apr 06 2014 Hello guys/girls,
• anonymous (17/25) Apr 06 2014 I'd advise you to avoid casts, especially when you're starting
• monarch_dodra (8/11) Apr 06 2014 Well, conversion to int "drops" the fractional part, rounding

"Daniele M." <gdm85 iragan.com> writes:

Hello guys/girls,


I have read almost completely the book and I am very much 
interested in D language. However sometimes I have doubts that I 
cannot clearly cut out, thus I thought it would be a good idea to 
ask the community.

For example, is this the best way to perform a conversion + floor?
Input 'x' is a floating point expression that is never big enough 
to justify usage of double or real type, but I picked "real" 
because I noticed that it was the implicit cast type.

auto s = "3.14";
int x = cast(int)floor(to!real(x));
// x == 3

Thanks in advance!
--
   Daniele

"anonymous" <anonymous example.com> writes:

On Sunday, 6 April 2014 at 08:23:16 UTC, Daniele M. wrote:

 For example, is this the best way to perform a conversion + 
 floor?

 Input 'x' is a floating point expression that is never big 
 enough to justify usage of double or real type, but I picked 
 "real" because I noticed that it was the implicit cast type.

 auto s = "3.14";
 int x = cast(int)floor(to!real(x));

(assuming you meant to!real(s) here)

 // x == 3

I'd advise you to avoid casts, especially when you're starting
out with D. They're unsafe and you can easily blow your leg off
with them. std.conv.to does safe conversions. So, use to!int
instead of cast(int).

Conversion to int drops the fractional part, so you don't really
need floor. But if you think it makes the intent clearer, feel
free to leave it in.

With UFCS[1], dropped empty parentheses, and 'auto' for implicit
typing:

auto x = s.to!real.to!int;

You could try to avoid the double conversion and parse directly 
to int. But that would be a lot more work and error-prone, if you 
want to support all the formats that to!real recognizes. I think 
two conversions are fine.

[1] http://dlang.org/function.html#pseudo-member

"monarch_dodra" <monarchdodra gmail.com> writes:

On Sunday, 6 April 2014 at 09:23:21 UTC, anonymous wrote:
 Conversion to int drops the fractional part, so you don't really
 need floor. But if you think it makes the intent clearer, feel
 free to leave it in.

Well, conversion to int "drops" the fractional part, rounding 
*towards* 0, whereas floor floor will reduce to the lower 
integral.

It can make a difference for negatives:

auto x = -3.5;
floor(x); // => -4
cast(int)x; // => -3