/// <summary>
/// Convert angle (in degrees) into a DMS string (using d, ', and ").
/// </summary>
/// <param name="angle">input angle (degrees)</param>
/// <param name="trailing"><see cref="TrailingUnit"/> value indicating the trailing units of the string (this component is given as a decimal number if necessary).</param>
/// <param name="prec">the number of digits after the decimal point for the trailing component.</param>
/// <param name="ind"><see cref="HemisphereIndicator"/> value indicating additional formatting.</param>
/// <param name="dmssep">if not <c>0</c>, use as the <see cref="DMS"/> separator character (instead of d, ', " delimiters).</param>
/// <returns>formatted string</returns>
/// <remarks>
/// The interpretation of <paramref name="ind"/> is as follows:
/// <list type="bullet">
/// <item><paramref name="ind"/> == <see cref="HemisphereIndicator.None"/>,
/// signed result no leading zeros on degrees except in the units place, e.g., <c>-8d03'</c>.</item>
/// <item><paramref name="ind"/> == <see cref="HemisphereIndicator.Latitude"/>,
/// trailing N or S hemisphere designator, no sign, pad degrees to 2 digits, e.g., <c>08d03'S</c>.
/// </item>
/// <item><paramref name="ind"/> == <see cref="HemisphereIndicator.Longitude"/>,
/// trailing E or W hemisphere designator, no sign, pad degrees to 3 digits, e.g., <c>008d03'W</c>.
/// </item>
/// <item><paramref name="ind"/> == <see cref="HemisphereIndicator.Azimuth"/>,
/// convert to the range [0, 360°), no sign, pad degrees to 3 digits, e.g., <c>351d57'</c>.
/// </item>
/// </list>
/// The integer parts of the minutes and seconds components are always given with 2 digits.
/// </remarks>
public static string Encode(double angle, TrailingUnit trailing, int prec, HemisphereIndicator ind = HemisphereIndicator.None, char dmssep = '\0')
{
// Assume check on range of input angle has been made by calling
// routine (which might be able to offer a better diagnostic).
if (!IsFinite(angle))
{
return(angle < 0 ? "-inf" :
(angle > 0 ? "inf" : "nan"));
}
// 15 - 2 * trailing = ceiling(log10(2^53/90/60^trailing)).
// This suffices to give full real precision for numbers in [-90,90]
prec = Min(15 + 0 - 2 * (int)trailing, prec);
var scale = 1d;
for (var i = 0; i < (int)trailing; ++i)
{
scale *= 60;
}
for (var i = 0; i < prec; ++i)
{
scale *= 10;
}
if (ind == HemisphereIndicator.Azimuth)
{
angle -= Floor(angle / 360) * 360;
}
int sign = angle < 0 ? -1 : 1;
angle *= sign;
// Break off integer part to preserve precision in manipulation of
// fractional part.
double
idegree = Floor(angle),
fdegree = (angle - idegree) * scale + 0.5;
{
// Implement the "round ties to even" rule
var f = Floor(fdegree);
fdegree = (f == fdegree && (f % 2) == 1) ? f - 1 : f;
}
fdegree /= scale;
if (fdegree >= 1)
{
idegree += 1;
fdegree -= 1;
}
Span <double> pieces = stackalloc[] { fdegree, 0, 0 };
for (var i = 1; i <= (int)trailing; ++i)
{
double
ip = Floor(pieces[i - 1]),
fp = pieces[i - 1] - ip;
pieces[i] = fp * 60;
pieces[i - 1] = ip;
}
pieces[0] += idegree;
var s = new StringBuilder();
if (ind == HemisphereIndicator.None && sign < 0)
{
s.Append('-');
}
var w = 0;
switch (trailing)
{
case TrailingUnit.Degree:
if (ind != HemisphereIndicator.None)
{
w = 1 + Min((int)ind, 2) + prec + (prec != 0 ? 1 : 0);
}
s.Append(pieces[0].ToFixedString(prec).PadLeft(w, '0'));
// Don't include degree designator (d) if it is the trailing component.
break;
default:
if (ind != HemisphereIndicator.None)
{
w = 1 + Min((int)ind, 2);
}
s.Append(pieces[0].ToString().PadLeft(w, '0'))
.Append(dmssep != 0 ? dmssep : char.ToLower(dmsindicators_[0]));
switch (trailing)
{
case TrailingUnit.Minute:
w = 2 + prec + (prec != 0 ? 1 : 0);
s.Append(pieces[1].ToFixedString(prec).PadLeft(w, '0'));
if (dmssep != 0)
{
s.Append(char.ToLower(dmsindicators_[1]));
}
break;
case TrailingUnit.Second:
s.AppendFormat("{0:D2}", (int)pieces[1])
.Append(dmssep != 0 ? dmssep : char.ToLower(dmsindicators_[1]))
.Append(pieces[2].ToFixedString(prec).PadLeft(2 + prec + (prec != 0 ? 1 : 0), '0'));
if (dmssep == 0)
{
s.Append(char.ToLower(dmsindicators_[2]));
}
break;
default:
break;
}
break;
}
if (ind != HemisphereIndicator.None && ind != HemisphereIndicator.Azimuth)
{
s.Append(hemispheres_[(ind == HemisphereIndicator.Latitude ? 0 : 2) + (sign < 0 ? 0 : 1)]);
}
return(s.ToString());
}
/// <summary>
/// Convert angle into a <see cref="DMS"/> string (using d, ', and ") selecting the trailing component based on the precision.
/// </summary>
/// <param name="angle">input angle (degrees)</param>
/// <param name="prec">the precision relative to 1 degree.</param>
/// <param name="ind"><see cref="HemisphereIndicator"/> value indicating additional formatting.</param>
/// <param name="dmssep">if not <c>0</c>, use as the <see cref="DMS"/> separator character (instead of d, ', " delimiters).</param>
/// <returns>formatted string</returns>
/// <remarks>
/// <paramref name="prec"/> indicates the precision relative to 1 degree, e.g., <paramref name="prec"/> = 3 gives a result accurate to 0.1' and
/// <paramref name="prec"/> = 4 gives a result accurate to 1". <paramref name="ind"/> is interpreted as in
/// <see cref="Encode(double, TrailingUnit, int, HemisphereIndicator, char)"/> with the additional facility that <see cref="HemisphereIndicator.Number"/>
/// represents angle as a number in fixed format with precision <paramref name="prec"/>.
/// </remarks>
public static string Encode(double angle, int prec, HemisphereIndicator ind = HemisphereIndicator.None, char dmssep = '\0')
=> ind == HemisphereIndicator.Number ? angle.ToFixedString(prec) :
Encode(angle,
prec < 2 ? TrailingUnit.Degree : (prec < 4 ? TrailingUnit.Minute : TrailingUnit.Second),
prec < 2 ? prec : (prec < 4 ? prec - 2 : prec - 4),
ind, dmssep);
