Convertions in C++

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);

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

Code:

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

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

Quote:

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

Code:

---

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

---

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

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Not if you inline then :)

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

Code:

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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;
}

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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 :)

Quote:

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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 :)

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

:D

Thanks!! you all... :)

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