*
* Project 4 due December 13th
* Final Exam is December 17th at 8:00 in 0135
EGR
* Complete course evaluations!
*
* Unions:
* Remember: unions ARE NOT structs- they can
only take on 1 value
* Ex.
* union
union_test{
char single_char;
char *mult_char;
int single_int;
int *mult_int;
}
*
* Accessing union values:
* The syntax looks just like it does for structs:
union_test.single_char=‘a’;
union_test.mult_char=“Hello!”;
* Remember: the struct can only take one value at
a time
* Consider keeping track of what kind of data is inside
the union, ex. poly-print.c
* **Hint** working with unions and exploiting the fact
that they can only have one value at a time could
be a part of a question on the final…
*
* Void pointers:
* Ex. void *mystery_data;
* Widely expand the use of an ADT
* Allows you to create an ADT that operates on some
unknown type of data.
* Tips:
* Don’t flip when you see a void **! (or a void ***)
void *data_field;
int extra;
Char extra2;
*
???
* Adds another level of flexibility
* Fantastic for loops with different conditions!
* Structure of function pointer is just like function declaration:
<output>(*<function pointer name>)(<input1>,<input2>,<input3>);
* Ex.
void (*insert_func)(int *, int, int);
*
* Another idea!
* What if we embed function pointers in an ADT?
* Ex. when a new struct variable is initialized you
could set that node’s functions as well.
* Warning: the syntax is terrible!
*
typedef struct new_data_{
int data1;
char data2;
struct new_data_ *next;
int print_func(struct new_data_*);
}new_data;
*
* Two parts to the project:
* Backend: create the ADT
* Use the ADT to implement a dictionary
* Pay close attention to the function
specifications
*
* Yes, abstract data types DO exist in C.
* Data type includes:
* Some type of data or representation of data
* Could be: primitives, structs, unions,
void pointers
* Specific functions to operate on the data
*
typedef struct rational_ {
int numerator;
int denominator;
} rational;
Just a struct
rational new_rat(int numerator, int
denominator);
rational add_rat(rational x, rational
rational sub_rat(rational x, rational
rational mul_rat(rational x, rational
rational div_rat(rational x, rational
void print_rat(rational x);
y);
y);
y);
y);
Functions to
be used with
the struct
*
* Someone OTHER than the author needs to be
able to use the ADT
* Ex. the best way to REALLY test project 4, give
your files to a friend and ask them to code with
it!
* Includes a full set of functions to use the
datatype
* Ex. Add, subtract, multiply (for integer like
datatypes), store, print, find (for memory
arrangements)
*
* Hiding functions that you DON’T want nonauthors to touch
* Some functions could do damage to different
aspects of a program’s implementation if called
incorrectly
* Use ‘static’ to restrict functions to the .c module
in which it’s declared
* Then it can’t be called from any other .c file!
*
* From
* http://www.cs.princeton.edu/courses/archive/spr9
6/cs217/precepts/adt-precept/
* Note: This program uses 3 different files
* Header: defines the struct and the different functions
provided
* Function .c module: includes the code for all of the
functions
* Function with main: makes use of the ADT designed in
the other two files
*