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Lecture 10
Let Implementation
T. METIN SEZGIN
NOV 9 2009
LET: our pet language
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An example program
 Input
 Scanning & parsing
 The AST
Components of the language
 Syntax
 Values
 Environment
 Behavior specification
 Behavior implementation
 Scanning
 Parsing
 Evaluation
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Syntax data types
Values
 Set of values manipulated by the program
 Expressed values


Possible values of expressions
Denoted values

Possible values of variables
 Interface for values
 Constructors
 Observers
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Environments
 Same model of environment from before
 Use
to abbreviate
Specifying the behavior
 Programs
 Expressions
 Constructors

Observer
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Specifying the behavior
 Programs
 Expressions
 Constructors

Observer
Specifying the behavior
 Programs
 Expressions
 Constructors

Observer
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Behavior implementation
what we envision
Behavior implementation
what we envision
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The Interpreter
The Interpreter
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