parsii.eval

Class Scope

java.lang.Object

parsii.eval.Scope

All Implemented Interfaces:

Serializable

public class Scope
extends Object
implements Serializable

Contains a mapping of names to variables.

Both the user as well as the Parser use a Scope to resolve a name into a Variable. In contrast to a simple Map, this approach provides two advantages: It's usually faster, as the variable only needs to be resolved once. Modifying it and especially reading it when evaluating an expression is as cheap as a simple field access. The second advantage is that scopes can be chained. So variables can be either shared by two expression or kept separate, if required.

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
static Scope	create() Creates a new empty scope.
Variable	create(String name) Searches or creates a variable in this scope.
static Scope	createWithParent(Scope parent) Creates a new scope with the given parent.
Variable	find(String name) Searches for a Variable with the given name.
Set<String>	getLocalNames() Returns all names of variables known to this scope (ignoring those of the parent scope).
Collection<Variable>	getLocalVariables() Returns all variables known to this scope (ignoring those of the parent scope).
Set<String>	getNames() Returns all names of variables known to this scope or one of its parent scopes.
Variable	getVariable(String name) Searches for or creates a variable with the given name.
Collection<Variable>	getVariables() Returns all variables known to this scope or one of its parent scopes.

Methods inherited from class java.lang.Object

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

Method Detail

create

public static Scope create()

Creates a new empty scope.

The scope will not be completely empty, as Math.PI (pi) and Math.E (E) are always defined as constants.

Returns:

a new scope and empty

createWithParent

public static Scope createWithParent(Scope parent)

Creates a new scope with the given parent.

If a variable is resolved, first the own scope is scanned. If no variable for the given name is found, the parent scope is scanned. If this yields a variable, it will be returned. Otherwise it will be defined in the local scope (not in the parent).

Parameters:

parent - the scope to use as lookup source for further variables

Returns:

a new scope with the given parent as super scope

find

public Variable find(String name)

Searches for a Variable with the given name.

If the variable does not exist null will be returned

Parameters:

name - the name of the variable to search

Returns:

the variable with the given name or null if no such variable was found

getVariable

public Variable getVariable(String name)

Searches for or creates a variable with the given name.

If no variable with the given name is found, a new variable is created in this scope

Parameters:

name - the variable to look for

Returns:

a variable with the given name

create

public Variable create(String name)

Searches or creates a variable in this scope.

Tries to find a variable with the given name in this scope. If no variable with the given name is found, the parent scope is not checked, but a new variable is created.

Parameters:

name - the variable to search or create

Returns:

a variable with the given name from the local scope

getLocalNames

public Set<String> getLocalNames()

Returns all names of variables known to this scope (ignoring those of the parent scope).

Returns:

a set of all known variable names

getNames

public Set<String> getNames()

Returns all names of variables known to this scope or one of its parent scopes.

Returns:

a set of all known variable names

getLocalVariables

public Collection<Variable> getLocalVariables()

Returns all variables known to this scope (ignoring those of the parent scope).

Returns:

a collection of all known variables

getVariables

public Collection<Variable> getVariables()

Returns all variables known to this scope or one of its parent scopes.

Returns:

a collection of all known variables