Fix compilation on ARM based systems (#1093)

* Handle case where 0 is passed to FloatWidth()

* Change FloatWidth() function to MinNumFracChars(). FloatWidth() was a
misleading name; the original intent was to ensure when writing out
coordinates with a certain step size that the precision was large enough
to accomodate the step (e.g. a step of .001 would need at least a
precision of 3). Also rework the function so it is more accurate for
values that are not exactly powers of 10.

* 6.28.0. Minor revision bump for fixes for ARM; may also slightly affect
  (fix) the output precision of certain X step values in output ASCII
data formats in some cases.

src/StringRoutines.cpp

@@ -93,12 +93,20 @@ int DigitWidth(long int numberIn) {
   return (minusSign + numi);
 }
 
-// FloatWidth()
-/** \return the number of characters necessary to express given float. */
-int FloatWidth(double floatIn) {
-  double float_exponent = fabs( log10( floatIn ) );
-  ++float_exponent;
-  return (int)float_exponent; // Cast to int implicitly rounds down
+/** \return the number of characters necessary for a minimal representation of
+  *         the fractional part of a floating point number, i.e. the number of
+  *         leading zeros plus 1. characters necessary to express given float.
+  */
+int MinNumFracChars(double floatIn) {
+  // Split number into integer and fractional part
+  double intpart = 0;
+  double frac = modf(floatIn, &intpart);
+  // Leading zeros
+  int n_leading_zeros = 0;
+  double absfrac = fabs(frac);
+  if (absfrac > 0)
+    n_leading_zeros = (int)ceil( fabs( log10( absfrac ) ) ) - 1;
+  return n_leading_zeros + 1;
 }
 
 // ---------- STRING CONVERSION ROUTINES --------------------------------------- 

src/StringRoutines.h

@@ -15,8 +15,8 @@ std::string AppendNumber(std::string const &, int);
 int WildcardMatch(std::string const&, std::string const&);
 /// \return number of characters needed to represent given digit.
 int DigitWidth(long int);
-/// \return number of characters needed to represent given floating point.
-int FloatWidth(double);
+/// \return Min number of chars needed to represent fractional part of given floating point.
+int MinNumFracChars(double);
 /// Remove any trailing whitespace from string.
 void RemoveTrailingWhitespace(std::string &);
 /// \return string stripped of trailing whitespace.

src/TextFormat.cpp

@@ -59,7 +59,7 @@ void TextFormat::SetCoordFormat(size_t maxFrames, double min, double step,
   int col_width = DigitWidth( (long int)maxCoord );
   // Check if the precision is enough to support the step size.
   if (step < 1.0) {
-    int prec_exp_width = FloatWidth( step );
+    int prec_exp_width = MinNumFracChars( step );
     if (prec_exp_width > col_precision)
       col_precision = prec_exp_width;
   }

src/Version.h

@@ -12,7 +12,7 @@
  * Whenever a number that precedes <revision> is incremented, all subsequent
  * numbers should be reset to 0.
  */
-#define CPPTRAJ_INTERNAL_VERSION "V6.27.3"
+#define CPPTRAJ_INTERNAL_VERSION "V6.28.0"
 /// PYTRAJ relies on this
 #define CPPTRAJ_VERSION_STRING CPPTRAJ_INTERNAL_VERSION
 #endif