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>> DAVID J. MALAN: Let's now implement a
function that doesn't just have a side

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effect, but instead returns
a return value.

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Specifically, let's implement a function
called get positive int whose

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purpose in life is to do exactly that.

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Specifically, I'd like to use
this function as follows--

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int N gets get positive int.

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And then print f, thanks
for the percent i as a

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placeholder, comma, end.

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>> Now of course, get positive
int doesn't yet exist.

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So let's promise to implement it by
adding to the top of my file a line

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like int signifying that this function
will return in int--

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get positive int.

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And let's specify explicitly that this
function will not take any input, and

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so its arguments are void.

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Let's now at the bottom of my file,
simply so that I can keep main up top,

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actually implement or define
this function.

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>> First we start with the same
signature, so to speak--

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int get positive int void.

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And now let's implement get
positive int as follows.

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Let's declare an int, also called N but
we could call it almost anything

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we'd like, do the following while some
condition is true, and we'll return to

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that condition in a moment.

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Print f, please give me a positive int,
and now let's use Get int from

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the CS50 library to actually
get that int.

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>> But in my condition, let's do this
loop so long as N is less than 1.

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In other words, so long as the user
does not cooperate by providing me

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with a positive int, let me re-prompt
him or her again, and again, and again

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until he or she does.

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But I'm not done yet, because at the
end of this function I need to

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actually do something with that input.

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And so I'm going to go about returning
it with a line like return end

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semicolon, thereby returning an actual
int to main who called this function.

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Now it's worth noting that even though
get positive int returns in int, it's

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certainly fine for it to return
a positive int specifically.

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There isn't a special data type for
positive integer specifically, so we

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simply use the built in "int."

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>> Now back at line nine, notice that I'm
printing out N. But the N in this line

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belongs to the N that's declared
in line eight.

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So it turns out you can absolutely have
variables identically named so

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long as they exist within
different scopes.

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And recall that scope is defined by
the curly braces that most closely

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surround the variable
that you've defined.

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>> Now let's compile and
run this program.

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Make functions 1, dot
slash functions 1.

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Let's give it a positive int-like 50,
and it says thanks for the 50.

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Meanwhile, if we don't cooperate,
running the program again, giving it

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0, I'm prompted again, or giving it
negative 1, I'm prompted again.

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But if I do cooperate providing it with,
say, 50, I'm thanked for the 50.

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