Lecture 27 - November 29, 2007
Returned some work
Quiz on chapter 7
Chapter 9 -
fundamentals of subprograms
·
subprogram
o definition
o calls
o active
o header
o parameter profile (signature)
o protocol
(signature + return value)
o prototype (like the
·
parameters
o formal parameters
o actual parameters
o positional parameters
o keyword parameters (named parameters)
·
subprogram
types
o procedures
(e.g. subroutines in FORTRAN)
o functions
(i.e. methods in Java)
·
important
questions
o parameter passing method(s) used
o are types of actual and formal checked
o are local variables statically or
dynamically allocated
o if subprograms can be passed as parameters
and subprograms can be nested, what is the referencing environment of a passed subprogram?
o can subprograms be overloaded
function “<”
( a, b : in myArray) is
result :
boolean;
Begin
Result :=
true;
for I in myArray’first .. myArray’last loop
if
(a(i) >= b(i) ) then
Result := false;
End
if;
End loop;
Return result;
End “<”;
Myboolean :=
“<”(myArrayA, myArrayB);
o can subprograms be generic
·
local
variables
·
parameter-passing
methods
o formal parameters are characterized by one
of three distinct semantics models
§
they
can received data from the corresponding actual parameter
§
they
can transmit (send) data to the actual parameter
§
they
can do both
o pass by value
o pass by result
o pass by value/result
o pass by reference
o pass by name
o
·
which
languages use which parameter passing mode
o C uses pass by value but can get pass by
reference using pointers as parameters
o
o FORTRAN uses pass by reference
o Pascal uses pass by value, pass by
reference
o C# uses pass by value but can achieve pass
by reference
·
type
checking of parameters
·
multi-dimensional
arrays as parameters
·
parameters
that are subprogram names
·
overloaded
subprograms
·
generic
subprograms
Parameter passing
modes
