- Parameter variables
are variables defined in the parameter list of a function:
Example: float RectangleRule(float f(float), float a, float b, int N) { ... } int main(int argc, char *argv[]) { ... }
- Purpose of Parameter Variables:
- To receive values (=information) from
outside the
method
- More technically:
Parameters is a mechanism to pass a value from a scope into another scope
Schematically:
- To receive values (=information) from
outside the
method
- A concrete example:
- Method2()
has a variable
x
defined
inside its scope
- Method2() passes (making the variable available) x into the scope of Method1()
- Method2()
has a variable
x
defined
inside its scope
- There are
2 parameters
involved in a
function call
- The
parameter variable
in the
function definition
is called the
formal parameter
- The
parameter variable
in the
function call
is called the
actual parameter
- Schematically:
- Formal
and
actual parameters
are matched according
to their
position
in the function definition and
function invocation
- "Function invocation" = function call, or the use of the function.
- Lifetime of a parameter variable:
- A parameter variable
begins to exist
at the
beginning of the function
- A parameter variable ends to exist at the end of the function
- A parameter variable
begins to exist
at the
beginning of the function
- Scope of a parameter variable:
- The scope of a parameter variable
starts
at the
beginning of the function
NOTE: it is also initialized with the actual parameter when it is first defined !
- The scope of a parameter variable ends at the end of the function
- The scope of a parameter variable
starts
at the
beginning of the function
- NOTE:
-
In C/C++, you are allowed to
define a variable
with the same name
as a
parameter variable
In that case, the parameter variable is overshadowed
- NOTE:
Java does NOT allow you to shadow parameter variables.
- Conclusion on parameter variables::
Parameter variables behaves the same way as local variables defined at the beginning of a method