All Packages  Class Hierarchy  This Package  Previous  Next  Index

Class epp.Symbol

java.lang.Object
   |
   +----epp.Token
           |
           +----epp.Symbol

public class Symbol

extends Token

Symbol is an important data type that is used for many purposes in EPP. The followin are examples of the usage of Symbol.

	Symbol x = :foo;
	Symbol y = :"foo";
	Symbol z = Symbol.intern("foo");
	System.out.println(x == :foo);	// true
	System.out.println(y == :foo);	// true
	System.out.println(z == :foo);	// true

In expressions, Symbols are expressed as a colon followed by an identifier as in :foo. The portion following the colon is called "the name of the Symbol". Names with symbol characters and spaces can also be expressed by enclosing the name of the Symbol with double quotes as in :"." or :"long name".

Symbols can be compared using the == operator. The result will be true if the name of the two Symbols match.

Symbols can also be used as keys of java.util.Hashtable. It is faster than using strings as keys.

The Symbol class is actually a subclass of class Token, and is used as result values of the lexical analyzer.

Symbol is used for many purposes in the source code of EPP, including the following.

• Tokens that describe identifiers and symbols
• Tags that describe the type of the node of an abstract syntax tree
• Keys of hash tables such as MacroTable and EmitterTable
• Variable names of dynamic variables

See Also:

Token, Tree, Dynamic

Symbol()

intern(String)

Converts a string into a Symbol.

isSymbol()

Returns true if this token is a Symbol and false otherwise.

main(String[])

maybeIdentifier()

setMaybeIdentifierFlag()

toString()

Converts a Symbol into a string.

 public Symbol()

 public static Symbol intern(String name)

Converts a string into a Symbol.

 public String toString()

Converts a Symbol into a string.

Overrides:

toString in class Object

 public boolean isSymbol()

Returns true if this token is a Symbol and false otherwise.

Overrides:

isSymbol in class Token

See Also:

Token

 public void setMaybeIdentifierFlag()

 public boolean maybeIdentifier()

 public static void main(String argv[])

All Packages  Class Hierarchy  This Package  Previous  Next  Index