I found this piece of code and I am trying to figure out how it works, but I don't understand the part after the return statement. Can somebody explain this?
int f(int y)
{
return (y<=1)?1:y*f(y-1);
}
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9read about conditional or ternary operators. – Sourav Ghosh Oct 26 '16 at 14:58
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1It is a recursive function. – Weather Vane Oct 26 '16 at 14:59
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fibonacci or something? – Jean-François Fabre Oct 26 '16 at 15:00
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2Factorial is my guess. – Weather Vane Oct 26 '16 at 15:00
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"If y is less than or equal to 1 then return 1 else return y times f(y-1)" – 001 Oct 26 '16 at 15:00
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Ye its pretty insefficient version of factorial – Tomasz Plaskota Oct 26 '16 at 15:00
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2When you say you want help figuring it out, can you please be more specific? There are three things going on: The ternary expression (the `?:` bit), the recursion (the call again to `f`), and the algorithm itself. Which is it you have trouble figuring out? – Some programmer dude Oct 26 '16 at 15:01
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2Might also get trouble with *integer overflow*. – Weather Vane Oct 26 '16 at 15:01
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1It should be noted that this is a very bad way to write programs. Not only is the algorithm hard to read, it also makes the program needlessly inefficient. As a rule of thumb, only use recursion as a very last resort. It has very limited practical use. Unfortunately books and teachers spend far too much time teaching about such a useless, inefficient, dangerous feature. – Lundin Oct 26 '16 at 15:17
1 Answers
4
This:
int f(int y)
{
return (y<=1) ? 1 : y*f(y-1);
}
is equivalent to this:
int f(int y)
{
if(y <= 1)
{
return 1;
} else
{
return y*f(y-1);
}
}
which should be clear to you by now, that it's a recursive function that uses The ternary (conditional) operator in C.
The ternary operator has this general form:
condition ? a : b
where if condition evaluates into True, then a will be executed, else b.
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Remove the braces around `(condition)`. They are not part of the syntax. – Paul Ogilvie Oct 26 '16 at 15:16
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Also (see that only now): remove the `;`. (`;` is a statement terminator and turns an expression into a statement, but this is only an expression, so _no_ `;`) – Paul Ogilvie Oct 26 '16 at 16:00