CSC195, Class 21: Functions in C

Overview
* Function basics
* C functions vs. Java functions
* Q and A
* Lab

Notes
* Read Gries!
* Don't leave your empties in the MathLAN
* Silly story about Sam's trips.
* Since it's taken so long for me to write the exam, 
  I'm cancelling it.
  (You will only have two exams this semester, plus an 
  optional final.)
* Are there any questions about the pointers lab?

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Functions in C

What is a function?
* A construct that takes in values and returns others.
* A named and parameterized collection of code.

What do functions look like in C?

<type> <name-of-function>(<parameter-list>)
{
  <sequence-of-statements>
}

You can have an empty parameter list.
You can have an empty procedure body.
You can have no type (in which case it defaults to "int").
You probably need a name.

What do functions look like in Java?
<modifiers> <type> <name-of-function>(<parameter-list>)
  <optional-throws-clause>
{
  <sequence-of-statements>
}
Some modifiers: static public private protected final

C also has some modifiers, but we'll ignore them for now.

In C, it's a *really good idea* to declare functions before
you use them.  In Java, you don't usually declare functions
separately from their use (interfaces and abstract classes
provide some declaration-like capabilities).

Java forces you to type things.

Java allows you to throw exceptions.
* Exceptions can be used to provide precondition checking
* Allow the procedure to select the control flow used upon
  returning from the procedure.

Do the short and sketchy lab.

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REFLECTION

* Does the compiler check the type or number of the parameters?
* Does your friend splint?

* Warnings do not stop our compiler from compiling.
* The implicit return type of any undeclared procedure is
  int.
* What do you expect our compiler or splint to say for
  gecko(1);
  gecko(1.1);
* Explanation of extern, static, ...
* Tail recursion:
  The only thing you do after a recursive call is
   return its value.