Convertions in C++

[Eena]

What is the most efficient way to write a funtion (InchesToYards), expecting inches and returns yards, using the following prototypes:

int inchesToFeet (int inches);
int FeetToYards (int feet);

[CornedBee]

do you mean you already have those functions? If so, then this would be the easiest:

int inchesToYards(int inches)
{
  return FeetToYards(inchesToFeet(inches));
}

But it would be faster in execution to rewrite the conversion.

[kedaman]

Originally posted by CornedBee
do you mean you already have those functions? If so, then this would be the easiest:

int inchesToYards(int inches)
{
  return FeetToYards(inchesToFeet(inches));
}

But it would be faster in execution to rewrite the conversion.

Not if you inline then

[CornedBee]

even if he inlines them. I don't know inches, yards and feet, so I'll make a metric example:

inline int MmToM(int mm)
{ return mm*1000; }
inline int MToKm(int m)
{ return m*1000; }

// now what is faster?
int MmToKmA(int mm)
{
  return MToKm(MmToM(mm);
}
// becomes:
// return mm*1000*1000;
int MmToKmB(int mm)
{
  return mm*1000000;
}

A good compiler may optimize that away, but if not, the second would be slightly faster. It doesn't matter really, unless you're counting femtoseconds

[parksie]

Originally posted by CornedBee
A good compiler may optimize that away, but if not, the second would be slightly faster. It doesn't matter really, unless you're counting femtoseconds

Well, you've got at least 10 extra clock cycles, what with the pop, skip, and a jmp

[Eena]

Thanks!! you all...

I quess there are several ways to slice and dice this conversion...