On Friday, 28 April 2017 at 16:42:28 UTC, Petar Kirov
[ZombineDev] wrote:
On Friday, 28 April 2017 at 16:24:55 UTC, Suliman wrote:
On Friday, 28 April 2017 at 15:45:25 UTC, Suliman wrote:
I am using https://github.com/mysql-d/mysql-native
It's return from DB variant data-type.
My DB include value: 56.051151 (double type in DB)
I need to extract it. I tried several variants:
writeln(point[3].coerce!float);
writeln(point[3].coerce!string);
writeln(point[3].coerce!double);
but all of them return me it as: 56.0512
How to return exactly 56.051151 ?
import std.stdio;
import std.variant;
void main()
{
Variant b = 56.051151;
float x = b.coerce!float;
writeln(x);
}
56.0512
The precision is still there, you're just not requesting it:
import std.conv : text;
import std.stdio;
import std.variant;
void main()
{
Variant b = 56.051151;
float x = b.coerce!float;
foreach (i; 0 .. 10)
writefln(text("%.", i, "f"), x);
}
56
56.1
56.05
56.051
56.0512
56.05115
56.051151
56.0511513
56.05115128
56.051151276
How to return exactly 56.051151 ?
Specify the number of digits after the decimal point manually,
e.g. writefln("%.6f", x) will print 56.051151.
BTW, you should always try to use the same floating-point type,
so if you use 64-bit doubles in the database, you should also use
double in your D code, otherwise you may accumulate rounding
errors after each conversion. When converting to smaller
floating-point types (real -> double and double -> float) you are
essentially throwing out precision. For example:
import std.conv : text;
import std.stdio;
import std.variant;
void main()
{
Variant b = 56.051151;
foreach (i; 0 .. 16)
{
writefln(text("%.", i, "f"), b.coerce!float);
writefln(text("%.", i, "f"), b.coerce!double);
}
}
Notice how the floats and doubles differ at i >= 6.
56
56
56.1
56.1
56.05
56.05
56.051
56.051
56.0512
56.0512
56.05115
56.05115
56.051151
56.051151
56.0511513
56.0511510
56.05115128
56.05115100
56.051151276
56.051151000
56.0511512756
56.0511510000
56.05115127563
56.05115100000
56.051151275635
56.051151000000
56.0511512756348
56.0511510000000
56.05115127563477
56.05115100000000
56.051151275634766
56.051150999999997
