CIS 3020 Part 3 - Revision history

Jka: /* Scope */

2008-01-23T22:07:31Z

Scope

Jka: /* Example */

2007-03-30T14:12:54Z

Example

Jka: /* Scope */

2007-03-23T16:55:26Z

Scope

Jka: /* Implementation */

2007-03-23T16:52:29Z

Implementation

Jka: /* Logical Operators */

2007-03-23T16:43:10Z

Logical Operators

Jka: /* Alternative Implementation 3 */

2007-03-23T16:42:25Z

Alternative Implementation 3

Jka: /* Flow Charts */

2007-03-23T16:25:17Z

Flow Charts

Jka: /* Truth Tables */

2007-02-27T17:42:20Z

Truth Tables

Jka: /* Truth Tables */

2007-02-27T17:39:18Z

Truth Tables

Jka: /* Truth Tables */

2007-02-27T17:34:09Z

Truth Tables

@@ Line 414: / Line 414: @@
 |}
 * Which is easier to understand?
 ==Continue with [[CIS 3020 Part 4]]==

@@ Line 375: / Line 375: @@
+}
 </pre>
-* But, an arbitray order is bad:
+* But, an arbitrary order is bad:
 <pre>
 if (percScore < 60) {
@@ Line 390: / Line 390: @@
 </pre>
 * What grade is a score of 69?
 ==Scope==
 * Note that {}'s denote scope.

← Older revision		Revision as of 16:55, 23 March 2007
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	\|}		\|}
	* Which is easier to understand?		* Which is easier to understand?
		+	==Continue with [[CIS 3020 Part 4]]==

← Older revision		Revision as of 16:52, 23 March 2007
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	}		}
	</pre>		</pre>
		+	=='''if-else-if''' Ladder==
		+	* This is a common programming structure when a series of tests must be performed:
		+	<pre>
		+	if (expr_1) {
		+	stmt_1;
		+	} else if (expre_2) {
		+	stmt_2;
		+	} else if ...
		+	</pre>
		+	* As soon as an expression is found to be true, you evaluate the associated statement and quit.
		+	===Example===
		+	* Suppose that we are calculating final grades for this class:
		+	<pre>
		+	if (percScore >= 90) {
		+	grade="A";
		+	} else if (percScore >= 80) {
		+	grade="B";
		+	} else if (percScore >= 70) {
		+	grade="C";
		+	} else if (percScore >= 60) {
		+	grade="D";
		+	} else {
		+	grade="E";
		+	}
		+	</pre>
		+	* Note: Order is critical!
		+	* We can also do the following:
		+	<pre>
		+	if (percScore < 60) {
		+	grade="E";
		+	} else if (percScore < 70) {
		+	grade="D";
		+	} else if (percScore < 80) {
		+	grade="C";
		+	} else if (percScore < 90) {
		+	grade="B";
		+	} else {
		+	grade="A";
		+	}
		+	</pre>
		+	* But, an arbitray order is bad:
		+	<pre>
		+	if (percScore < 60) {
		+	grade="E";
		+	} else if (percScore < 80) {
		+	grade="C";
		+	} else if (percScore < 70) {
		+	grade="D";
		+	} else if (percScore < 90) {
		+	grade="B";
		+	} else {
		+	grade="A";
		+	}
		+	</pre>
		+	* What grade is a score of 69?
		+	==Scope==
		+	* Note that {}'s denote scope.
		+	* They are often used (as above) to clarify what is included in the "then" and "else"...
		+	{\| border="1"
		+	! This: !! Is equivalent to:
		+	\|-
		+	\|
		+	<pre>
		+	if (x>=0) {
		+	abs=x;
		+	} else {
		+	abs=-x;
		+	}
		+	</pre>
		+	\|\|
		+	<pre>
		+	if (x>=0)
		+	abs=x;
		+	else
		+	abs=-x;
		+	</pre>
		+	\|}
		+	* Which is easier to understand?

@@ Line 295: / Line 295: @@
 | & || Returns true if both are true (tests both)
 |-
-| &#124&#124 || Returns true if either are true (short circuit)
+| &#124;&#124; || Returns true if either are true (short circuit)
 |-
-| &#124 || Return true if either are true (tests both)
+| &#124; || Return true if either are true (tests both)
 |-
 | ! || Negation operation
@@ Line 305: / Line 305: @@
 (((a<=b)&&(c==d))||!(a==d+2))
 </pre>
 ==Example - Maximum==
 * Suppose that we are given two values, first and second, and wish to find their maximum.

← Older revision		Revision as of 16:42, 23 March 2007
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	</pre>		</pre>
	<center>''NOTE: BAD to use multiple returns!''</center>		<center>''NOTE: BAD to use multiple returns!''</center>
		+	==Relational Operators==
		+	Java supports several relational operators:
		+	{\| border="1"
		+	! Operator !! Definition
		+	\|-
		+	\| == \|\| equality
		+	\|-
		+	\| != \|\| not equal
		+	\|-
		+	\| > \|\| greater than
		+	\|-
		+	\| >= \|\| greater than or equal
		+	\|-
		+	\| < \|\| less than
		+	\|-
		+	\| <= \|\| less than or equal
		+	\|}
		+	All return a boolean value of true or false.
		+	==Logical Operators==
		+	Java supports several logical operators for combining results of relational operations:
		+	{\| border="1"
		+	! Operator !! Definition
		+	\|-
		+	\| && \|\| Returns true if both are true (short circuit)
		+	\|-
		+	\| & \|\| Returns true if both are true (tests both)
		+	\|-
		+	\| &#124&#124 \|\| Returns true if either are true (short circuit)
		+	\|-
		+	\| &#124 \|\| Return true if either are true (tests both)
		+	\|-
		+	\| ! \|\| Negation operation
		+	\|}
		+	Use:
		+	<pre>
		+	(((a<=b)&&(c==d))\|\|!(a==d+2))
		+	</pre>
		+	==Example - Maximum==
		+	* Suppose that we are given two values, first and second, and wish to find their maximum.
		+	* Create a specification, design, and implementation.
		+	===Specification===
		+	{\| border="1"
		+	\| Inputs \|\| first, second
		+	\|-
		+	\| Outputs \|\| The larger of first or second
		+	\|-
		+	\| Constraints \|\| None
		+	\|-
		+	\| Assumptions \|\| None
		+	\|-
		+	\| Relationships \|\| None
		+	\|}
		+	===Design===
		+	# Given first and second
		+	# If first is larger than second, return first
		+	# if second is larger than first, return second
		+	# What if they are equal?
		+	===Implementation===
		+	<pre>
		+	public int max(int first, int second) {
		+	int maxi=second;
		+	if (first>second)
		+	maxi = first;
		+	return maxi;
		+	}
		+	</pre>

← Older revision		Revision as of 16:25, 23 March 2007
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	* Diamonds - represent decision to make		* Diamonds - represent decision to make
	* Lines with arrows - detail the "flow" within the diagram		* Lines with arrows - detail the "flow" within the diagram
		+	===Example===
		+	* Suppose we have a value, x, and would like to calculate the absolute value of x, setting '''absol''' to this value:
		+	<pre>
		+	if (x>=0) {
		+	absol=x;
		+	} else {
		+	absol=-x;
		+	}
		+	</pre>
		+	* This is not real useful unless we need this calculated only once, so as a method we might write:
		+	<pre>
		+	public int abs(int) {
		+	int absol;
		+	if (x>=0) {
		+	absol=x;
		+	} else {
		+	absol = -x;
		+	}
		+	return (absol);
		+	}
		+	</pre>
		+	====Alternative Implementation 1====
		+	<pre>
		+	public int abs(int x) {
		+	if (x<0) {
		+	x=-x;
		+	}
		+	return (x);
		+	}
		+	</pre>
		+	====Alternative Implementation 2====
		+	<pre>
		+	public int abs(int x) {
		+	if (x<0) {
		+	return (-x);
		+	} else {
		+	return (x);
		+	}
		+	}
		+	</pre>
		+	<center>''NOTE: BAD to use multiple returns!''</center>
		+	====Alternative Implementation 3====
		+	<pre>
		+	public int abs(int x) {
		+	if (x<0) {
		+	return (-x);
		+	}
		+	return (x);
		+	}
		+	</pre>
		+	<center>''NOTE: BAD to use multiple returns!''</center>

← Older revision		Revision as of 17:42, 27 February 2007
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	\| F F \|\| T \|\| F \|\| F		\| F F \|\| T \|\| F \|\| F
	\|}		\|}
		+	! is a Unary operator - takes a single value<br>
		+	&& and \|\| are Binary operators - take two values
		+	==Flow Charts==
		+	Flow charts are used to visually express what a program does
		+
		+	Major components of a Flow Chart:
		+	* Boxes - represent calculations to perform
		+	* Diamonds - represent decision to make
		+	* Lines with arrows - detail the "flow" within the diagram

@@ Line 198: / Line 198: @@
 ====Truth Tables====
 {| border="1"
-! A B !! !A !! A && B !! A "||" B
+! A B !! !A !! A && B !! A &#124;&#124; B
 |-
 | T T || F || T || T