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Averages/Mean time of day: Difference between revisions
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The mean time is : 23:47:43
</pre>
=={{header|D}}==
{{trans|Python}}
<lang d>import std.stdio, std.range, std.algorithm, std.complex, std.math,
std.format, std.conv;
double radians(in double d) pure nothrow @safe @nogc {
return d * PI / 180;
}
double degrees(in double r) pure nothrow @safe @nogc {
return r * 180 / PI;
}
double meanAngle(in double[] deg) pure nothrow @safe @nogc {
return (deg.map!(d => fromPolar(1, d.radians)).sum / deg.length).arg.degrees;
}
string meanTime(in string[] times) pure @safe {
auto t = times.map!(times => times.split(':').to!(int[3]));
assert(t.all!(hms => 24.iota.canFind(hms[0]) &&
60.iota.canFind(hms[1]) &&
60.iota.canFind(hms[2])),
"Invalid time");
auto seconds = t.map!(hms => hms[2] + hms[1] * 60 + hms[0] * 3600);
enum day = 24 * 60 * 60;
const to_angles = seconds.map!(s => s * 360.0 / day).array;
immutable mean_as_angle = to_angles.meanAngle;
auto mean_seconds_fp = mean_as_angle * day / 360.0;
if (mean_seconds_fp < 0)
mean_seconds_fp += day;
immutable mean_seconds = mean_seconds_fp.to!uint;
immutable h = mean_seconds / 3600;
immutable m = mean_seconds % 3600;
return "%02d:%02d:%02d".format(h, m / 60, m % 60);
}
void main() @safe {
["23:00:17", "23:40:20", "00:12:45", "00:17:19"].meanTime.writeln;
}</lang>
{{out}}
<pre>23:47:43</pre>
=={{header|Erlang}}==
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