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/* -*- mode: objc; coding: utf-8 -*- */
/* Étoilisp/Mulklisp, a Common Lisp subset for the Étoilé runtime.
* Copyright (C) 2008 Matthias Andreas Benkard.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or (at
* your option) any later version.
*
* This program 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 the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#import <Foundation/NSArray.h>
#import <Foundation/NSDictionary.h>
#import <Foundation/NSNull.h>
#import "MLKEnvironment.h"
#import "MLKUndefinedVariableException.h"
static id UNBOUND;
@implementation MLKEnvironment
+(void) initialize
{
UNBOUND = [[NSObject alloc] init];
}
-(MLKEnvironment *) init
{
return [self initWithParent:nil bindings:nil];
}
-(MLKEnvironment *) initWithParent:(MLKEnvironment *)parent bindings:(NSDictionary *)bindings
{
self = [super init];
_bindings = [[NSMutableDictionary alloc] initWithCapacity:10];
ASSIGN (_parent, parent);
[self addBindings: bindings];
return self;
}
-(MLKEnvironment *) initWithParent:(MLKEnvironment *)parent
{
return [self initWithParent:parent bindings:nil];
}
-(MLKEnvironment *) initWithBindings:(NSDictionary *)bindings
{
return [self initWithParent:nil bindings:bindings];
}
-(MLKEnvironment *) parent
{
return _parent;
}
-(void) setValue:(id)value forBinding:(MLKSymbol *)symbol;
{
[self setBinding:symbol to:value inEnvironment:self];
}
-(void) setBinding:(MLKSymbol *)symbol to:(id)value inEnvironment:(MLKEnvironment *)env
{
value = value ? value : (id) [NSNull null];
if ([_bindings objectForKey:symbol])
[_bindings setObject:value forKey:symbol];
else
if (_parent)
[_parent setBinding:symbol to:value inEnvironment:env];
else
[[[MLKUndefinedVariableException alloc] initWithEnvironment:env
variableName:symbol]
raise];
}
-(id) valueForBinding:(MLKSymbol *)symbol
{
return [self valueForBinding:symbol inEnvironment:self];
}
-(id) valueForBinding:(MLKSymbol *)symbol inEnvironment:(MLKEnvironment *)env
{
id value;
if ((value = [_bindings objectForKey:symbol]))
{
if (value == [NSNull null])
return nil;
else if (value == UNBOUND)
[[[MLKUndefinedVariableException alloc] initWithEnvironment:env
variableName:symbol]
raise];
else
return value;
}
else
if (_parent)
return [_parent valueForBinding:symbol];
else
[[[MLKUndefinedVariableException alloc] initWithEnvironment:env
variableName:symbol]
raise];
return nil; // avoid a stupid compiler warning
}
-(void) addBindings:(NSDictionary *)bindings
{
[_bindings addEntriesFromDictionary:bindings];
}
-(void) addValue:(id)value forBinding:(MLKSymbol *)symbol;
{
value = value ? value : (id) [NSNull null];
[_bindings setObject:value forKey:symbol];
}
-(void) addBinding:(MLKSymbol *)symbol
{
[_bindings setObject:UNBOUND forKey:symbol];
}
-(MLKEnvironment *) environmentForBinding:(MLKSymbol *)symbol
{
if ([_bindings objectForKey:symbol])
return self;
else if (_parent)
return [_parent environmentForBinding:symbol];
else
return nil;
}
-(BOOL) boundp:(MLKSymbol *)symbol
{
id value;
if ((value = [_bindings objectForKey:symbol]))
return (value != UNBOUND);
else if (_parent)
return [_parent boundp:symbol];
else
return NO;
}
-(void) makunbound:(MLKSymbol *)symbol
{
if ([_bindings objectForKey:symbol])
[_bindings setObject:UNBOUND forKey:symbol];
else if (_parent)
return [_parent makunbound:symbol];
}
-(void) dealloc
{
RELEASE (_bindings);
RELEASE (_parent);
[super dealloc];
}
@end
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