201801 CSE240 Lecture 05
0 likes79 views
This document summarizes a lecture on data types and type checking in programming languages. It discusses basic data types like integers and floats, how they define the size and format of values, and type checking to ensure operands for operators have legal types. It also covers type equivalence based on structure or name, type conversion through coercion and casting, and how strong typing in languages like Java helps catch errors but reduces flexibility compared to weakly typed languages like Lisp. The next topics to be covered are programming with Java and C, including data types, input/output, pointers, and struct types.
![Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 7
Data Types Equivalence (Complex Types)
class Foo {
int data[100];
int count;
}
class Bar {
int data[100];
int count;
}
Foo x, y;
Bar r, s;
// name
// equivalence
// correct
x = y;
r = s;
// incorrect
x = r;
// structural
// equivalence
// correct
x = y;
r = s;
// correct
x = r;](https://image.slidesharecdn.com/cse240cl05data-180313074052/85/201801-CSE240-Lecture-05-7-320.jpg)
201801 CSE240 Lecture 05
- 1. CSE240 – Introduction to Programming Languages Lecture 05: Data, Data types and Type Checking Javier Gonzalez-Sanchez javiergs@asu.edu javiergs.engineering.asu.edu Office Hours: By appointment
- 2. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 2 Data | Memory management
- 3. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 3 Data Types • A set of primary values allowed and operations on these values. • Data types define size and format – used to declare variables. // Java int (4) (-231 to 231 ) ; -2,147,483,648 to 2,147,483,647 float (4) 3.4e−038 to 3.4e+038
- 4. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 4 Data Types • A set of primary values allowed and operations on these values. • Data types define size and format – used to declare variables. 00000000000000000000000000000011int i = 3; 01000000010000000000000000000000float j = 3.0f; sign exponent fraction
- 5. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 5 Type Checking (semantic) • Ensuring that the types of operands of an operator are legal or equivalent to the legal type. "Hello" + 5; 5 > 7 + “Hello” char x = 60 + 5; float a = 2.0; double b = 2.0; int b = 'a';
- 6. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 6 Data Types Equivalence (Complex Types) • Structural equivalence Two types are equivalent if they have the same set of values and operations. • Name equivalence Two types are equivalent if they have the same name
- 7. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 7 Data Types Equivalence (Complex Types) class Foo { int data[100]; int count; } class Bar { int data[100]; int count; } Foo x, y; Bar r, s; // name // equivalence // correct x = y; r = s; // incorrect x = r; // structural // equivalence // correct x = y; r = s; // correct x = r;
- 8. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 8 § Coercion –implicitly convert Type_A to Type_B. § Casting: –explicitly convert Type_A to Type_B. § Type error. Type Conversion
- 9. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 9 Type Conversion int x = 5; // Coercion: Implicit type conversion (int to float) float f = 3.14f + x; // Casting: Explicit type conversion (float to int) int i = (int) f + x;
- 10. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 10 A strongly typed language is one in which: § each name in a program has a single type associated with it; § the type is known at compilation time; § type errors are always reported. StrongWeak C C++ Java Strong Type Checking
- 11. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 11 A strongly typed language is one in which: § each name in a program has a single type associated with it; § the type is known at compilation time; § type errors are always reported. Strong Type Checking Is strong type checking good? ☐ Yes ☐ No ☐ Maybe
- 12. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 12 A strongly typed language is one in which: § each name in a program has a single type associated with it; § the type is known at compilation time; § type errors are always reported. Strong Type Checking Is strong type checking good? Trade flexibility for reliability! Strong type increase reliability, but it loses the flexibility. float x = 3.0f; // Java float x = 3.0; // C (defvar x 3.0) // LISP
- 13. Javier Gonzalez-Sanchez | CSE 240 | Fall 2017 | 13 Homework Homework 1: Programming with Java Next lecture: Programming with C Read Chapter 2 Topics: data types, input/output, pointers, struct type
- 14. CSE240 – Introduction to Programming Languages Javier Gonzalez-Sanchez javiergs@asu.edu Fall 2017 Disclaimer. These slides can only be used as study material for the class CSE240 at ASU. They cannot be distributed or used for another purpose.