map function support for floats and improved integer scaling

teensy3/WMath.cpp

@@ -40,11 +40,6 @@ int32_t random(int32_t howsmall, int32_t howbig)
 	return random(diff) + howsmall;
 }
 
-long map(long x, long in_min, long in_max, long out_min, long out_max)
-{
-	return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
-}
-
 unsigned int makeWord(unsigned int w) { return w; }
 unsigned int makeWord(unsigned char h, unsigned char l) { return (h << 8) | l; }
 

teensy3/WProgram.h

@@ -55,7 +55,28 @@ uint32_t random(uint32_t howbig);
 int32_t random(int32_t howsmall, int32_t howbig);
 void randomSeed(uint32_t newseed);
 void srandom(uint32_t newseed);
-long map(long, long, long, long, long);
+
+#include <type_traits>
+// when the input number is an integer type, do all math as 32 bit signed long
+template <class T, class A, class B, class C, class D>
+T map(T _x, A _in_min, B _in_max, C _out_min, D _out_max, typename std::enable_if<std::is_integral<T>::value >::type* = 0)
+{
+	long x = _x, in_min = _in_min, in_max = _in_max, out_min = _out_min, out_max = _out_max;
+	// Arduino's traditional algorithm
+	//return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
+	// st42's suggestion: https://github.com/arduino/Arduino/issues/2466#issuecomment-69873889
+	if ((in_max - in_min) > (out_max - out_min)) {
+		return (x - in_min) * (out_max - out_min+1) / (in_max - in_min+1) + out_min;
+	} else {
+		return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
+	}
+}
+// when the input is a float or double, do all math using the input's type
+template <class T, class A, class B, class C, class D>
+T map(T x, A in_min, B in_max, C out_min, D out_max, typename std::enable_if<std::is_floating_point<T>::value >::type* = 0)
+{
+	return (x - (T)in_min) * ((T)out_max - (T)out_min) / ((T)in_max - (T)in_min) + (T)out_min;
+}
 
 #include "pins_arduino.h"