Principles of Programming

1
Principles of Programming
With examples in JavaScript and odd pseudo-code

• Zachary Young

2
Contents

• Variables
• Operators
• Conditionals
• Loops
• Functions
• Programming Habits
• Introduction to Complexity Analysis

3
Common Variable Types

• Integer
• Float
• Boolean
• Character
• String
• Array

• var integer 100
• var float 3.1415
• var boolean TRUE
• var character a
• var string hello world
• var arr array( 1, 2, 3 )

4
Complex Types

• Vector
• (Linked) List
• Stack
• Queue

Arrays are vectors in JavaScript Not many complex
types in JavaScript, but one could create them
5
Complex Types 2

• Different types have different advantages and
  disadvantages
• Vectors are good for random access, but not for
  dynamic resizing
• Lists work well when dynamic resizing is
  important, but do not work well with random
  access.

6
Objects

• Represent objects (items) in the real world.
• Structures Classes in most languages
• Simply Objects in JavaScript
• Document Object Model (DOM) in JavaScript

7
Variable Typing

• Strong Typing
• C
• A variable is declared to be of a certain type
  and does not change except by coercion.
• Weak Typing
• Most web languages (including JavaScript)
• Variables are only briefly associated with a type.

8
Operators

• Mathematical
• Addition ( )
• Subtraction ( - )
• Multiplication ( )
• Division ( / )
• Modulus ( )
• Assignment ( )
• Variations ( , --, , - )

• Conditional
• And ( )
• Or ( )
• Not ( ! )
• Equal ( )
• Not Equal ( !, ltgt )

9
Conditional Statements

• If Elseif Else
• stmt1 ? stmt2 third
• If stmt1 is true, then do stmt2, otherwise do
  stmt3
• Switch statements

• if ( zach great )
• document.write( correct )
• elseif ( zach awesome )
• document.write( right! )
• else
• document.write( WRONG )
• printval ( (zach great ) ? correct (
  zach awesome ) ? right WRONG )
• document.write( printval )

10
Looping

• For
• While
• Do While

• for ( lcv 0 lcv lt 100lcv)
• document.write( lcv )
• while( lcv lt 100 )
• document.write( lcv )
• lcv
• lcv 0
• do
• document.write( lcv )
• lcv
• while( lcv lt 100 )

11
Functions

• Provide modular way of performing repeated tasks
• One task per function
• Usually the shorter the better

• function zachgreat ( var zach )
• alert( zach )
• var f function( x ) alert( x )
• this method is not very useful in JavaScript

12
Passing Variables

• Pass-by-reference
• Memory address of the original variable is passed
  to the function.
• (not available in JavaScript)

• Pass-by-value
• Copy of the variable is passed to the function.

13
Good Programming Habits

• Plan before you code
• Use descriptive variable names
• Use comments
• Small modular functions
• Use consistent style
• Brackets
• Naming conventions

14
Complexity Analysis

• Big O Notation
• Analyzes worst case scenario
• Denoted by
• O( 1 ), O( n ), O( n2 ), etc
• Usually only worry about highest order term
• limn-gt8 O( n3 n2 ) n3

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Conclusion

• Plan first!
• Be consistent!
• Delve deeper!
• Regular expressions
• Context-free grammars
• Design patterns