# Recursion stopping condition

Staff Emeritus
Science Advisor
Gold Member
I just finished writing a little recursive function in C++ and when my stopping condition is reached, I need it to do nothing. So the if statement looks funny:

if (the condition is met)
{
//do nothing
}
else
{
call yourself with smaller arguments
}

It works fine, but I feel uneasy about having absolutely nothing in the
if{} portion.
Is this bad programming style? Is it potentially dangerous?
Thanks!

## Answers and Replies

AlephZero
Science Advisor
Homework Helper
IMO the original is OK - the //do nothing comment makes it clear it means what it says.

You could write

if (! the condition is met)
{
do something;
}

Or possibly

if (the condition is met)
return;
else
{
do something;
}

Staff Emeritus
Science Advisor
Gold Member
Thanks, AZ!

I just finished writing a little recursive function in C++ and when my stopping condition is reached, I need it to do nothing. So the if statement looks funny:

if (the condition is met)
{
//do nothing
}
else
{
call yourself with smaller arguments
}

It works fine, but I feel uneasy about having absolutely nothing in the
if{} portion.
Is this bad programming style? Is it potentially dangerous?
Thanks!

It might be better for you to make your recurrence condition slightly different, so that you don't even need an else statement. That way both the 'if' and the 'else' statements can have a purpose, you might not even need the else statement.

D H
Staff Emeritus
Science Advisor
It might be better for you to make your recurrence condition slightly different, so that you don't even need an else statement.

For example,
Code:
if (! done) {
do_something_recursively;
}

However, in some circles that place an emphasis on high-quality programming, the lack of an else is seen as a sign that something may be awry. If no else is needed, such programmers would write the above as
Code:
if (! done) {
do_something_recursively;
} else {
; /* Null else */
}
to show that the algorithm designer/programmer has indeed deemed that no else is needed rather than merely forgotten.

Sure. Either way. Depends on style and acceptance.

verty
Homework Helper
I like to have the exit cases before the recursive ones, so for me the original is perfect, just how I would have done it.

Staff Emeritus
Science Advisor
Gold Member
Thanks for your advice on this, everyone. I appreciate it.