Booleans
And (& &)
< boolean > & & < boolean > -- < boolean >
Returns true if both inputs are true, and returns false if not.
EXAMPLES:
boolean x = true;
boolean y = false;
boolean z = x & & y;
boolean w = x & & x;
|
boolean z is a false statement since x is true and y is false.
boolean w is a true statement since x is true.
a -- 7
b -- 4
c -- 10
int a = IO.read_int ();
int b = IO.read_int ();
int c = IO.read_int ();
boolean x = (a < c) & & (a < b);
|
a < c is a true statement since 7 is less than 10..
a < b is a false statement since 7 is not less than 4..
Therefore the entire statement is false.
Or (| |)
< boolean > | | < boolean > -- < boolean >
Returns true if at least one input is true, and returns false otherwise.
Not (! )
! < boolean > -- < boolean >
Returns ``the other boolean.''
SAMPLE PROGRAM USING BOOLEANS:
/ /Read three integers.
int a = IO.read_int ();
int b = IO.read_int ();
int c = IO.read_int ();
/ /Perform comparisons and display results.
if ((a < b) & & (b < c))
{
print (a, b, c);
}
else if ((a < c) & & (c < b))
{
print (a, c, b);
}
static private print (int x, int y, int z)
{
IO.println (x + ````+ y + ````+ z);
}
|
Definition
ITERATION is the act of repeating a construct, or a slight variation on a construct, again and again in some controlled fashion.
There are three main mechanisms of iteration:
- ``while''
- ``for''
- ``recursion''
Definition
A WHILE STATEMENT is a repetition construct in which the thing being repeated is repeated while some condition is true.
EXAMPLE: (Counter control loop)
/ /Read and write four integers.
int i = 1;
while (i < = 4)
{
int x = IO.read_int ();
IO.println (x);
i = i + 1;
}
|
EXAMPLE: (Data control loop)
/ /Read several nonzero integers and print them.
int number = IO.read_int ();
while (! (number == 0))
{
IO.println (number);
number = IO.read_int ();
}
|
Definition
A COUNTER CONTROL LOOP is a repetition construct which is characterized by apriori knowledge of how many times the instruction block is to be run.
Counter control loops are controlled by a counter which governs the behavior of the loop.
Definition
A DATA CONTROL LOOP is a repetition construct which is governed by ``metadata'' accompanying the data being processed.
Definition
INCREMENTAL PROGRAMMING is a programming methodology wherin on develops a program by writing a sequence of programs with the following properties:
- The first program in the sequence performs some essentially trivial task, but which is fundamental to completion of the ultimate task.
- The last program in the sequence performs the task of ultimate interest.
- Each successor program performs a task only marginally more ellaborate than its predecessor.
