org.eclipse.golo.compiler

Class SymbolGenerator

java.lang.Object

org.eclipse.golo.compiler.SymbolGenerator

public final class SymbolGenerator
extends java.lang.Object

Name generator for synthetic objects.

The generated name follows the patter __$$_<name>_<counter>. The default name is symbol.

The generator maintains a stack of scope names, to generate hierarchical names.

 SymbolGenerator sym = new SymbolGenerator("closure");
 sym.current(); // __$$_closure_0
 sym.next(); // __$$_closure_1
 sym.current(); // __$$_closure_1
 sym.enter("scope");
 sym.next(); // __$$_closure_scope_2
 sym.enter("subscope");
 sym.next(); // __$$_closure_scope_subscope_3
 sym.exit().exit();
 sym.next(); // __$$_closure_4
 

Since the counter maintains uniqueness, the name and scopes only purpose is to give somewhat readable names to help debugging.

Be warned that the uniqueness is only preserved in the context of a single generator. Two independent generators with the same name (and scope) can produce identical names.

A counter is used instead of e.g. the generation timestamp or a random number to guarantee stability across compilations to ease debugging.

If a true uniqueness is require, or if the somewhat predictability of the symbol is a concern, one can use getFor(String) or even next(String) in conjunction with System.nanoTime() or Random.nextLong() (for instance sym.next(String.valueOf(System.nanoTime()))

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	DEFAULT_NAME
static java.lang.String	ESCAPE_MANGLE
static java.lang.String	JOIN
static java.lang.String	PREFIX

Constructor Summary

Constructors

Constructor and Description
SymbolGenerator()
SymbolGenerator(java.lang.String name)

Method Summary

Modifier and Type	Method and Description
java.lang.String	current() Generate the name for the current context.
java.lang.String	current(java.lang.String name) Generate the name for the current context and given simple name.
SymbolGenerator	enter(java.lang.String scopeName) Enter a hierarchical scope.
SymbolGenerator	exit() Exit from a scope.
java.lang.String	getFor(java.lang.String localName) Mangles the given name without using the counter.
java.lang.String	next() Generates the next name for the current context.
java.lang.String	next(java.lang.String name) Generates the next name for the current context and given simple name.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

PREFIX

public static final java.lang.String PREFIX

See Also:

Constant Field Values

DEFAULT_NAME

public static final java.lang.String DEFAULT_NAME

See Also:

Constant Field Values

ESCAPE_MANGLE

public static final java.lang.String ESCAPE_MANGLE

See Also:

Constant Field Values

JOIN

public static final java.lang.String JOIN

See Also:

Constant Field Values

Constructor Detail

SymbolGenerator

public SymbolGenerator(java.lang.String name)

SymbolGenerator

public SymbolGenerator()

Method Detail

next

public java.lang.String next()

Generates the next name for the current context.

Increments the counter and returns the name generated by the current scope and counter.

Returns:

the next name

next

public java.lang.String next(java.lang.String name)

Generates the next name for the current context and given simple name.

Increments the counter and returns the name generated by the given name and the current scope and counter, and increment it.

Warning: no check is made that the given name will produce a valid language symbol.

Parameters:

name - the simple name to derive the unique name from

Returns:

the corresponding next name

getFor

public java.lang.String getFor(java.lang.String localName)

Mangles the given name without using the counter.

This can be used in macros to provide hygiene by mangling the local variable names. Mangling is escaped for names beginning by ESCAPE_MANGLE.

For instance:

 let symb = SymbolGenerator("foo")
 symb: getFor("bar")  # __$$_foo_bar
 symb: getFor("$bar") # bar
 

Warning: no check is made that the given name will produce a valid language symbol.

current

public java.lang.String current(java.lang.String name)

Generate the name for the current context and given simple name.

Returns the name generated by the given name and the current scope and counter, without incrementing it.

Warning: no check is made that the given name will produce a valid language symbol.

Parameters:

name - the simple name to derive the unique name from

Returns:

the corresponding generated name

current

public java.lang.String current()

Generate the name for the current context.

Returns the name generated by the current scope and counter, without incrementing it.

Returns:

the generated name

exit

public SymbolGenerator exit()

Exit from a scope.

enter

public SymbolGenerator enter(java.lang.String scopeName)

Enter a hierarchical scope.

Warning: no check is made that the given name will produce a valid language symbol.

Parameters:

scopeName - the name of the scope.