Sather - A Language Manual

Abstract

Copyright Notice

This Documentation is covered by the GPL.

Copyright (C) 199x by International Computer Science Institute *** Copyright (C) 1999 by Free Software Foundation, Inc. *** This file is part of the GNU Sather package. It is free software; you may redistribute and/or modify it under the terms of the GNU General Public License (GPL) as published by the Free Software Foundation; either version 2 of the license, or (at your option) any later version. *** This file is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See Doc/GPL for more details. *** The license text is also available from: Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

Contents

• 1 Introduction
  • 1.1 Acknowledgements
  • 1.2 How to read this Document
  • 1.3 Sources of Information
  • 1.4 Obtaining the Compiler
    • 1.4.1 How do I ask questions?
  • 1.5 Summary of Features
    • 1.5.1 Basic Concepts
    • 1.5.2 Garbage Collection and Checking
    • 1.5.3 No Implicit Calls
    • 1.5.4 Separation of Subtyping and Code Inclusion
    • 1.5.5 Iterators
    • 1.5.6 Closures
    • 1.5.7 Immutable and Reference Objects
    • 1.5.8 IEEE Floating-Point
    • 1.5.9 pSather
  • 1.6 History
    • 1.6.1 The Name
    • 1.6.2 Sather's Antecedents
• 2 Classes and Objects
  • 2.1 Preliminaries
    • 2.1.1 Some basic classes - INT, FLT and STR
    • 2.1.2 Printing output
    • 2.1.3 Sather source files
    • 2.1.4 Hello World
  • 2.2 Defining Classes and Creating Objects
    • 2.2.1 Defining Simple Classes
    • 2.2.2 Checking whether an object has been created
    • 2.2.3 Types Introduced
    • 2.2.4 Hiding features: private and readonly
  • 2.3 Class Data: shared and const
    • 2.3.1 Shared Attributes - Restricted global variables
    • 2.3.2 Class Constants
    • 2.3.3 Accessing Class Data - the :: notation
  • 2.4 Routine definitions
    • 2.4.1 Routine Arguments and Modes
    • 2.4.2 Local Variables - Scoping and Shadowing
    • 2.4.3 Routine calls
    • 2.4.4 Simple Overloading - Selecting a routine to call
  • 2.5 Conditional Execution
    • 2.5.1 if statements
    • 2.5.2 case statements
    • 2.5.3 Short circuit boolean expressions: and and or
  • 2.6 Attribute Accessor Routines
    • 2.6.1 Attribute assignment
  • 2.7 Static Type Inference
    • 2.7.1 Creation Expressions
    • 2.7.2 Assignments and ::=
    • 2.7.3 Arguments to a function call
  • 2.8 Class Parameters
    • 2.8.1 Arrays
  • 2.9 A Running Example: Employees
• 3 Loops and Iterators
  • 3.1 Using iterators
    • 3.1.1 loop statements
    • 3.1.2 Built-in iterators
  • 3.2 Defining Iterators
    • 3.2.1 yield statements
    • 3.2.2 Explicitly leaving an iterator using quit
    • 3.2.3 Control flow within an iterator
    • 3.2.4 The once argument mode
    • 3.2.5 out and inout argument modes
    • 3.2.6 pre and post conditions in iterators
    • 3.2.7 Argument evaluation in iterators
    • 3.2.8 Points to note
  • 3.3 Iterator Examples
• 4 Code Inclusion and Partial Classes
  • 4.1 Include Clauses
    • 4.1.1 Renaming
    • 4.1.2 Multiple Inclusion
    • 4.1.3 Resolving conflicts
  • 4.2 Partial Classes and Stub routines
    • 4.2.1 Mixins: A Prompt Example
• 5 Abstract Classes and Subtyping
  • 5.1 Abstracting over Implementations
    • 5.1.1 Implementing a Stack using an Array
    • 5.1.2 A Stack Calculator
    • 5.1.3 A Linked List Representation of a Stack
    • 5.1.4 Switching Representations:Polymorphism
  • 5.2 Abstract Class Definitions
  • 5.3 Subtyping
    • 5.3.1 The Type Graph
    • 5.3.2 Dynamic Dispatch and Subtyping
  • 5.4 Supertyping
    • 5.4.1 Using supertyping
  • 5.5 Type Conformance
    • 5.5.1 Contravariant conformance
    • 5.5.2 Subtyping = substitutability
  • 5.6 The typecase statement
  • 5.7 The Overloading Rule
    • 5.7.1 Extending Overloading
    • 5.7.2 Permissible overloading
    • 5.7.3 Overloading as Statically resolved Multi-Methods
    • 5.7.4 Conflicts when subtyping
    • 5.7.5 Conflicts during code inclusion
    • 5.7.6 Points to note
    • 5.7.7 Overloading in Parametrized Classes
    • 5.7.8 Why not use the return type to resolve conflicts?
  • 5.8 When Covariance Ails You
    • 5.8.1 But don't animals eat food?
    • 5.8.2 Solution 1: Refactor the type hierarchy
    • 5.8.3 Solution 2: Eliminate the offending method
    • 5.8.4 Solution 3: Dynamically Determine the Type
    • 5.8.5 Solution 4: Parametrize by the Argument Type
• 6 Parametrized Classes and Arrays
  • 6.1 Parametrized concrete types
    • 6.1.1 Why Parametrize?
  • 6.2 Support for Arrays
    • 6.2.1 Array Access
    • 6.2.2 Array Classes: Including AREF and calling new();
    • 6.2.3 Standard Arrays: ARRAY{T}
    • 6.2.4 Multi-dimensional Arrays
  • 6.3 Type Bounds
    • 6.3.1 Why have typebounds?
    • 6.3.2 Supertyping and Type Bounds
  • 6.4 Parametrized Abstract Classes
  • 6.5 Overloading
    • 6.5.1 Overloading In the Parametrized Class Interface
    • 6.5.2 Overloading Resolution within the Parametrized Class
• 7 Operator Redefinition
  • 7.1 Method Names for Operators
  • 7.2 Operator expressions
    • 7.2.1 Operator precedence
  • 7.3 Array Access Routines
• 8 Immutable Classes
  • 8.1 Defining Immutable Classes
    • 8.1.1 Immutable Class Example
    • 8.1.2 Creating a new object
    • 8.1.3 Initial value of immutable objects
    • 8.1.4 Attribute access routines
    • 8.1.5 Points to note
  • 8.2 Using Immutable Classes
• 9 Closures
  • 9.1 Creating and Calling Closures
    • 9.1.1 Creating a closure
    • 9.1.2 Calling a closure
    • 9.1.3 Binding overloaded routines
    • 9.1.4 Points to note
    • 9.1.5 Binding some arguments
    • 9.1.6 Leaving self unbound
  • 9.2 Further Examples of Closures
    • 9.2.1 Closures for Applicative Programming
    • 9.2.2 Menu Structures
    • 9.2.3 Iterator closures
• 10 Exceptions
  • 10.1 Throwing and Catching Exceptions
    • 10.1.1 Throwing Exceptions with raise
    • 10.1.2 Catching Exceptions with protect
    • 10.1.3 Usage to avoid
    • 10.1.4 Alternatives to Exceptions
  • 10.2 A more elaborate example
• 11 Safety Features
  • 11.1 Preconditions
  • 11.2 Postconditions
    • 11.2.1 initial expressions
    • 11.2.2 result expressions
    • 11.2.3 Example
  • 11.3 Assertions
    • 11.3.1 assert statements
  • 11.4 Invariants
    • 11.4.1 The invariant routine
• 12 Built-in classes
  • 12.1 Fundamental Classes
    • 12.1.1 $OB
    • 12.1.2 Array support
  • 12.2 Tuples
  • 12.3 The SYS Class
  • 12.4 Object Finalization: $FINALIZE
  • 12.5 Basic Classes and Literal Forms
    • 12.5.1 Booleans and the BOOL class
    • 12.5.2 Characters and the CHAR class
    • 12.5.3 The string class, STR
    • 12.5.4 Integers and the INT class
    • 12.5.5 Infinite precision integers and the INTI class
    • 12.5.6 Floating point numbers: the FLT and FLTD classes
  • 12.6 Library Conventions
    • 12.6.1 Object Identity
    • 12.6.2 Nil and void
• 13 Interfacing with Fortran
  • 13.1 Overview
    • 13.1.1 External Fortran Call Example
    • 13.1.2 Overall Organization
  • 13.2 Name Binding
    • 13.2.1 Difficulties
    • 13.2.2 Implementation
  • 13.3 Datatype Mapping
    • 13.3.1 Scalar Types
    • 13.3.2 Fortran Array Classes
    • 13.3.3 F_ROUT and F_HANDLER Types
  • 13.4 Parameter Passing
    • 13.4.1 Return Types
    • 13.4.2 Argument Types
    • 13.4.3 OUT and INOUT Arguments
  • 13.5 Portability Issues
    • 13.5.1 Portability of the Interface Implementation Code
    • 13.5.2 Portability of the Generated Code
• 14 Interfacing with ANSI C
  • 14.1 Overall Organization
  • 14.2 Built-in C classes
  • 14.3 User-defined External C types
    • 14.3.1 Constants and C binding names
    • 14.3.2 Attributes and C structs
    • 14.3.3 Shared Attributes and C globals
  • 14.4 Parameter Passing
  • 14.5 Inlining C Code
• 15 Statement and Expression Catalogue
  • 15.1 Statements
    • 15.1.1 Assignment statements
    • 15.1.2 case statements
    • 15.1.3 if statements
    • 15.1.4 protect statements
    • 15.1.5 loop statements
    • 15.1.6 return statements
    • 15.1.7 typecase statements
    • 15.1.8 yield statements
    • 15.1.9 quit statements
  • 15.2 Expressions
    • 15.2.1 void expressions
    • 15.2.2 void test expressions
    • 15.2.3 Short circuit boolean expressions: and and or
    • 15.2.4 exception expressions