ix.util.lisp
Interface Interpreter.Env

All Known Implementing Classes:

Interpreter.AbstractEnv, Interpreter.GlobalEnv, Interpreter.LexicalEnv

Enclosing class:

Interpreter

public static interface Interpreter.Env

The context in which an expression is evaluated.

Method Summary

java.lang.Object	assign(Interpreter.VarRef ref, java.lang.Object val) Changes the value bound to the variable and then returns the new value.
Interpreter.Env	bind(Symbol[] vars, java.lang.Object[] vals) Returns a new Env in which the variables are bound to the corresponding values.
java.lang.Object	defaultValue() Returns the value that should be returned by expressions that do not have anything more appropriate to return.
boolean	isTrue(java.lang.Object value) Determines whether the object should be regarded as true; otherwise, the object is considered false.
java.lang.Object	lookup(Interpreter.VarRef ref) Returns the value bound to the variable by this environment.

Method Detail

lookup

java.lang.Object lookup(Interpreter.VarRef ref)

Returns the value bound to the variable by this environment.

Throws:

java.lang.Error - if the variable is not bound.

bind

Interpreter.Env bind(Symbol[] vars,
                     java.lang.Object[] vals)

Returns a new Env in which the variables are bound to the corresponding values.

Throws:

java.lang.Error - if there aren't exactly as many variables as values.

assign

java.lang.Object assign(Interpreter.VarRef ref,
                        java.lang.Object val)

Changes the value bound to the variable and then returns the new value. Note that this typically modifies an existing binding relationship rather than create a new one; however, a new one may be created, for instance if the variable is not already bound.

defaultValue

java.lang.Object defaultValue()

Returns the value that should be returned by expressions that do not have anything more appropriate to return.

isTrue

boolean isTrue(java.lang.Object value)

Determines whether the object should be regarded as true; otherwise, the object is considered false.