Contents Introduction Names Variables The Concept of Binding Type Checking Strong Typing Type Equivalence Scope Scope and Lifetime Referencing Environments Named Constants Introduction

Advantage: write ability

• Advantage: write ability
• Disadvantage: reliability (less trouble with Perl)

• Example of : Implicit Declaration in Perl

•Any name begins with $ is a scalar, which

can store either a string or a numeric value

•A name begins with @ is an array

•A name begins with a % is a hash structure

A variable is bound to a type when it is assigned a value in an assignment statement (at run time, take the type of the value on the right-hand side)

• A variable is bound to a type when it is assigned a value in an assignment statement (at run time, take the type of the value on the right-hand side)
• Ex. for dynamic type binding in JavaScript

list = [2, 4.33, 6, 8];

list = 17.3;

• Advantage: flexibility (generic program units)
• Disadvantages:
• High cost (dynamic type checking and interpretation)


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