BicycleCar

Types

pedal()pushAccelerator()

Stringdoubleint

Programming Language Types

3 3.0 4.04 “three” “four”

= 7= “threefour”

+ +/

= 0

/

= 0.75

BM

ISpr

eads

heet

AB

MIC

alcu

lato

rTyping Objects

Object Types

Primitive types Classes

Kinds of Types

Types

ABMISpreadsheet

AnotherBMISpreadsheet

Interfaces

BMISpreadsheet

Stringdouble int

Type = Set of operations

Object Vs Primitive Types

• Instances of object types are objects.

• Instances of primitive types are primitive values.

• Primitive types used to construct object types.

• ~ Atoms Vs Molecules

• Different set of rules.

• In Smalltalk no difference.

• C++ even worse.

Abstract Value Vs Representation

2.2 02.2

0.22E+1

LBS_IN_KG

Invoking Abstract Operation

profit - earnings

-earnings

Math.round(bmi)

binary,infix

unary, prefix

Arbitray, method invocation

Types and Assignment

double height = 1.77;

int weight = 70;

int weight = 70.0;

double height = 2;

int weight = “seventy”;

Primitive Types

• Constants (Literals & Named Constants)

• Assignment Rules

• Operations with Invocation Syntax

Mathematical Integers

int Range & Constants

{- .. +}

int {-231 .. (231 – 1)}

0-2147483648

2147483647 2

02

Integer.MAX_VALUE

Integer.MIN_VALUE

-2

+2

32 bits

Mathematical Real Numbers

double Range & Constants

double

2.2

0.22E+1

0.22

Double.MAX_VALUE

Double.MIN_VALUE .2

64 bits

02.20 2. 2

2.2E0 22E-1

Standardmantissa

.22E1 .22E-1

exponent

xEy = x * 10y

Mathematical Integers

Other Integer Subsets

{- .. +}

byte {-27 .. (27 – 1)}

Byte.MAX_VALUEByte.MIN_VALUE

short {-215 .. (215 – 1)}

Short.MAX_VALUEShort.MIN_VALUE

long {-263 .. (263 – 1)}

Short.MAX_VALUEShort.MIN_VALUE

8 bits

16 bits

64 bits

Mathematical Real Numbers

float Size & Constants

float 32 bits

Float.MAX_VALUE

Float.MIN_VALUE .2

Mixed Assignment

long l =70;

int

Safe & Automatically Converted

int long

double d = 70;

int double

70.0;

long l

int i = 70.6;

Cast

int double

Not Automatically Converted

(int)

cast

70;

float i = 70.6;(float)

float double

Assignment Rules

v e

Te Tv

v = e;

Te Tv

v = (Tv) e;

TvTe

!(Te Tv || Te Tv)

v = (Tv) e;

double d = 5;

int i = (int) 5.7; bool b = (bool) 5;

Narrower than

Wider than

Assignment Rules for Primitive Types

• If T1 narrower than T2 (Set of instances of T1 Set of instances of T2)

• Expression of type T1 can be assigned to Variable of type T2

• Expression of type T2 can be assigned to Variable of type T1 with cast.

Actual Parameter Assignment

double weight;

public void setWeight (double newWeight) {

weight = newWeight;

}

setWeight (70);

Actual Parameter Assignment

int intWeight;

public void setIntWeight (int newWeight) {

intWeight = newWeight;

}

setWeight (70.6);setWeight ((int)70.6);

Returning a Value

double weight;

public int getIntWeight () {

return weight;

}

Translated Into Assignment

double weight;

public int getIntWeight () {

return weight;

}

double weight;

public int getIntWeight () {

int getIntWeight = weight;

}

Internal Variable

Returning a Value

double weight;

public int getIntWeight () {

return(int) weight;

}

Primitive Types

• Constants (Literals & Named Constants)

• Assignment Rules

• Operations with Invocation Syntax

Int Arithmetic Operations

5/2 5 % 2

x == (x/y)*y x == (x / y) * y + (x % y)

5/2 2 5 % 2 1

Name Action Operands & ResultType(Signature)

+ add int, int int- subtract int, int int- negate int int* multiply int, int int/ int quotient int, int int% int remainder int, int int

double Arithmetic Operations

5.0/2.0 5.0/2.0 2.5

Name Action Operands & Result Type(Signature)

+ add double, double double- subtract (unary) double- subtract double, double double* multiply double, double double/ divide double, double double

Overflow

Integer.MAX_VALUE + 1 Integer.MAX_VALUE

Integer.MIN_VALUE - 1 Integer.MIN_VALUE

Double.MAX_VALUE + 1 Double.MAX_VALUE

Double.MIN_VALUE - 1 Double.MIN_VALUE

(double) Integer.MIN_VALUE - 1.0 double)( Integer.MIN_VALUE - 1.0

Overflow

10/0 Integer.MAX_VALUE

-10/0 Integer.MIN_VALUE

10.0/0.0 Double.POSITIVE_INFINITY

-10.0/0.0 Double.NEGATIVE_INFINITY

0/0 0

0.0/0.0 Double.NaN

Int Overflow

Double Overflow

Mixed Operations

5/2.0

narrower type converted

5.0/2.0

int i = (int) (5/2.0) int i =(int) (5.0/2.0) int i = (int) 2.5

int i = 2

double d = 5/(int) 2.0 double d = 5/2 double d = 2

double d = 2.0

Strong Vs Weak Typing

“hello” - 1

int minus

Legal under Weak Typing

Illegal under Strong Typing

anything goes

strict type rules

Misc Math Operations

Operations (invoked on Math) Signatureabs() double double, int intacos(), asin(), atan(), cos(), sin(), tan() double doublepow () double, double doubleexp(), log() double doubleround() double longrandom(), pi() doublesqrt() double double

Math.pi() Math.power(5,3) 53

int i = Math.round(5.9)

Math.round(5.9) (long) 6

int i = 6int i = (int) Math.round(5.9)

(int) Math.round(Integer.MAX_VALUE + 1.0) Integer.MAX_VALUE

(int) 5.9 5

boolean Constants

boolean

falsetrue

Relational Operations

5 == 5 true

5 == 4 false

5 >= 4 true

5 <= 4 false

5 != 5 false

5 != 4 true

Name Action Signature of intimplementation

Signature of doubleimplementation

== equal? int, int boolean double, double boolean!= not equal? int, int boolean double, double boolean> greater than? int, int boolean double, double boolean< less than? int, int boolean double, double boolean>= greater than or

equal?int, int boolean double, double boolean

<= less than or equal? int, int boolean double, double boolean

Boolean Vs Number Expressions

hoursWorked > MAX_HOURS

true if hoursWorked is greater than MAX_HOURS and false otherwise

boolean overWorked =

int earnings = hourlyWage*hoursWorked + BONUS

Boolean Property

Boolean Property Code (edit)

public boolean isOverWeight() {

return OVER_WEIGHT_BMI < getBMI();

}

Boolean Property Code

public final double HIGH_BMI == 25;

public boolean getOverWeight() {return getBMI() >

HIGH_BMI;}

Boolean Property Code

public final double HIGH_BMI == 25;

public boolean isOverWeight() {return getBMI() >

HIGH_BMI;}

Boolean Operations

!true false

!false true

true && true true

true && false false

Name(s) Action Signature! not boolean boolean&&, & and boolean, booleanboolean||, | or boolean, booleanboolean

false && true false

false && false false

true || true true

true || false true

false || true true

false || false false

Regular evaluation

Short-circuit evaluation

Short-Circuit Evaluation

false && (9654.34/323.13 > 32.34) false

true || (9654.34/323.13 > 32.34) true

Name(s) Action Signature! not boolean boolean&&, & and boolean, booleanboolean||, | or boolean, booleanboolean

Second operand not evaluated

false & (9654.34/323.13 > 32.34 false

true | (9654.34/323.13 > 32.34) true

Second operand evaluated

Short-Circuit Evaluation

false && (10/0) false

Name(s) Action Signature! not boolean boolean&&, & and boolean, booleanboolean||, | or boolean, booleanboolean

false & (10/0)

error in some languages

false && (10 / 0)

Complex Expressions

Sub-expression

false && 10 / 0

Operator evaluation order?

Operator Precedence

! - (T)* / %+ -> < <= >=== !=&|&&||

false && 10 / 0false && 10 / 0

- 5 - 4 -5 - 4

!true && false !true && false

5 / 4 * 3 5/4 * 3

true || false == false || true

true || false == false || true

(int) 5 / 2.0 (int) 5 / 2.0

unary cast

Operator Precedence (edit)

! - (T)* / %+ -> < <= >=== !=&|&&||

false && (10 / 0)false && 10 / 0

- 5 - 4 (-5) - 4

!true && false ( !true) && false

5 / 4 * 3 (5/4) * 3

true || false == false || true

true || (false == false) || true

(int) 5 / 2.0 ((int) 5) / 2.0

unary cast

Operator Precedence

! - (T)* / %+ -> < <= >=== !=&|&&||

false && (10 / 0)false && 10 / 0

- 5 - 4 (-5) - 4

!true && false (!true) && false

5 / 4 * 3 (5/4) * 3

true || false == false || true

true || (false == false) || true

(int) 5 / 2.0 ((int) 5) / 2.0

unary cast

Printing Arbitrary Expressions

System.out.println (2) Output: 2

System.out.println (2.0) Output: 2.0

System.out.println ((int) 2.0) Output: 2

System.out.println (5 > 0) Output: true