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CS 112 Introduction to
Programming
Lecture #12:
Methods, Classes, and Objects
http://flint.cs.yale.edu/cs112/
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Recap
rExamples
mReverseNumber
mGamePlay
mIntLargest
mIntSnd
mTriangle
rDesigning a loop
mLook for a pattern/state
mDetermine termination condition
mSet correct initial state
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Outline
rAdmin. and review
ØClasses and Methods
rObjects: a first introduction
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Classes/Methods
rC# Framework Class Library (FCL) defines many classes, e.g.,
mConsole
mMessageBox
mInt32
mMath
rThe definition of a class includes both methods and data
properties:
mmethods, e.g.,
•Console.Write( )
•Console.WriteLine( )
•Int32.Parse( )
mproperties, e.g.,
•Int32.MinValue
•Int32.MaxValue
•Math.PI
•Math.E
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Methods
rA method should provide a well-defined, easy-to-
understand functionality
mA method takes input (parameters), performs some actions,
and (sometime) returns a value
rExample: invoking the WriteLine method of the
Console class:
Console.WriteLine ( "Whatever you are, be a good one.“ );
class method Information provided to the method
(parameters)
dot
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Example: Math Class Methods
Method Description Example
Abs( x ) absolute value of x Abs( 23.7 ) is 23.7
Abs( 0 ) is 0
Abs( -23.7 ) is 23.7
Ceiling( x )
rounds x to the smallest
integer not less than x Ceiling( 9.2 ) is 10.0
Ceiling( -9.8 ) is -9.0
Cos( x ) trigonometric cosine of x
(x in radians) Cos( 0.0 ) is 1.0
Exp( x ) exponential method ex Exp( 1.0 ) is approximately
2.7182818284590451
Exp( 2.0 ) is approximately
7.3890560989306504
Floor( x ) rounds x to the largest integer
not greater than x Floor( 9.2 ) is 9.0
Floor( -9.8 ) is -10.0
Log( x ) natural logarithm of x (base e)
Log( 2.7182818284590451 )
is approximately 1.0
Log( 7.3890560989306504 )
is approximately 2.0
Max( x, y ) larger value of x and y
(also has versions for float,
int and long values)
Max( 2.3, 12.7 ) is 12.7
Max( -2.3, -12.7 ) is -2.3
Min( x, y ) smaller value of x and y
(also has versions for float,
int and long values)
Min( 2.3, 12.7 ) is 2.3
Min( -2.3, -12.7 ) is -12.7
Pow( x, y ) x raised to power y (xy) Pow( 2.0, 7.0 ) is 128.0
Pow( 9.0, .5 ) is 3.0
Sin( x ) trigonometric sine of x
(x in radians) Sin( 0.0 ) is 0.0
Sqrt( x ) square root of x Sqrt( 900.0 ) is 30.0
Sqrt( 9.0 ) is 3.0
Tan( x ) trigonometric tangent of x
(x in radians) Tan( 0.0 ) is 0.0
Commonly used Math class methods.
