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Update math macros to avoid computing callable arguments more than once #391

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Update math macros to avoid computing callable arguments more than once #391

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38 changes: 32 additions & 6 deletions cores/arduino/Arduino.h
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Original file line number Diff line number Diff line change
Expand Up @@ -89,14 +89,40 @@ void yield(void);
#undef abs
#endif

#define min(a,b) ((a)<(b)?(a):(b))
#define max(a,b) ((a)>(b)?(a):(b))
#define abs(x) ((x)>0?(x):-(x))
#define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
#define round(x) ((x)>=0?(long)((x)+0.5):(long)((x)-0.5))
#ifdef __GNUC__
#define max(a,b) \
({ typeof (a) _a = (a); \
typeof (b) _b = (b); \
_a > _b ? _a : _b; })
#define min(a,b) \
({ typeof (a) _a = (a); \
typeof (b) _b = (b); \
_a < _b ? _a : _b; })
#define abs(a) \
({ typeof (a) _a = (a); \
_a > 0 ? _a : _a * -1; })
#define constrain(amt, low, high) \
({ typeof (amt) _amt = (amt); \
typeof (low) _low = (low); \
typeof (high) _high = (high); \
_amt < _low ? _low : _amt > _high ? _high : _amt; })
#define round(x) \
({ typeof (x) _x = (x); \
((_x)>=0?(long)((_x)+0.5):(long)((_x)-0.5)) })
#define sq(x) \
({ typeof (x) _x = (x); \
_x * _x })
#else
#define min(a,b) ((a)<(b)?(a):(b))
#define max(a,b) ((a)>(b)?(a):(b))
#define abs(x) ((x)>0?(x):-(x))
#define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
#define round(x) ((x)>=0?(long)((x)+0.5):(long)((x)-0.5))
#define sq(x) ((x)*(x))
#endif

#define radians(deg) ((deg)*DEG_TO_RAD)
#define degrees(rad) ((rad)*RAD_TO_DEG)
Comment on lines +123 to 125
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These two lines (124, 125 for radians and degrees) expose the very same problem as do all macro calls. Why not define them as inline constexpr functions instead? Like so:
'
template<typename T> inline constexpr T min(T a, T b) { return a > b ? b : a; }

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Because that doesn't work in C, and these macros are currently usable from C, so that would break compatibility.

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I was also concerned about binary size.

#define sq(x) ((x)*(x))

#define interrupts() sei()
#define noInterrupts() cli()
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