diff options
| -rw-r--r-- | MLKEnvironment.h | 9 | ||||
| -rw-r--r-- | MLKEnvironment.m | 76 |
2 files changed, 41 insertions, 44 deletions
diff --git a/MLKEnvironment.h b/MLKEnvironment.h index fe2be16..b40ea5a 100644 --- a/MLKEnvironment.h +++ b/MLKEnvironment.h @@ -3,12 +3,13 @@ #import "MLKLispValue.h" -@class NSMutableDictionary, MLKLinkedList, MLKSymbol; +@class NSMutableDictionary, MLKSymbol; @interface MLKEnvironment : MLKLispValue { - MLKLinkedList *_bindings; + MLKEnvironment *_parent; + NSMutableDictionary *_bindings; } -(MLKEnvironment *) init; @@ -20,4 +21,8 @@ -(void) addBinding:(MLKSymbol *)symbol to:(id)value; -(void) setBinding:(MLKSymbol *)symbol to:(id)value; -(id) valueForBinding:(MLKSymbol *)symbol; + +// Private methods. +-(void) setBinding:(MLKSymbol *)symbol to:(id)value inEnvironment:(MLKEnvironment *)env; +-(id) valueForBinding:(MLKSymbol *)symbol inEnvironment:(MLKEnvironment *)env; @end diff --git a/MLKEnvironment.m b/MLKEnvironment.m index e37c888..6df4e11 100644 --- a/MLKEnvironment.m +++ b/MLKEnvironment.m @@ -5,22 +5,19 @@ #import <Foundation/NSArray.h> #import "MLKEnvironment.h" -#import "MLKLinkedList.h" -#import "MLKCons.h" #import "MLKUndefinedVariableException.h" @implementation MLKEnvironment -(MLKEnvironment *) init { - _bindings = [[MLKLinkedList alloc] init]; - return self; + return [self initWithParent:nil bindings:nil]; } -(MLKEnvironment *) initWithParent:(MLKEnvironment *)parent bindings:(NSDictionary *)bindings { - _bindings = [[MLKLinkedList alloc] initWithCons:[parent->_bindings firstCons]]; - [_bindings push: [NSMutableDictionary dictionaryWithCapacity:10]]; + _bindings = [[NSMutableDictionary alloc] initWithCapacity:10]; + ASSIGN (_parent, parent); [self addBindings: bindings]; return self; } @@ -37,54 +34,49 @@ -(void) setBinding:(MLKSymbol *)symbol to:(id)value { - MLKCons *cons; - for (cons = [_bindings firstCons]; cons; cons = [cons cdr]) - { - NSMutableDictionary *dict = [cons car]; - if ([[dict allKeys] containsObject:symbol]) - { - [dict setObject:value forKey:symbol]; - break; - } - } - - [[[MLKUndefinedVariableException alloc] initWithEnvironment: self - variableName: symbol] - raise]; + [self setBinding:symbol to:value inEnvironment:self]; +} + +-(void) setBinding:(MLKSymbol *)symbol to:(id)value inEnvironment:(MLKEnvironment *)env +{ + if ([[_bindings allKeys] containsObject: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 { - MLKCons *cons; - for (cons = [_bindings firstCons]; cons; cons = [cons cdr]) - { - NSMutableDictionary *dict = [cons car]; - if ([[dict allKeys] containsObject:symbol]) - { - return [dict objectForKey:symbol]; - } - } + return [self valueForBinding:symbol]; +} - [[[MLKUndefinedVariableException alloc] initWithEnvironment: self - variableName: symbol] - raise]; - return nil; +-(id) valueForBinding:(MLKSymbol *)symbol inEnvironment:(MLKEnvironment *)env +{ + if ([[_bindings allKeys] containsObject:symbol]) + return [_bindings objectForKey:symbol]; + 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 { - int i; - NSArray *keys = [bindings allKeys]; - int count = [keys count]; - for (i = 0; i < count; i++) - { - [self addBinding:[keys objectAtIndex:i] to:[bindings objectForKey:[keys objectAtIndex:i]]]; - } + [_bindings addEntriesFromDictionary:bindings]; } -(void) addBinding:(MLKSymbol *)symbol to:(id)value { - NSMutableDictionary *dict = [[_bindings firstCons] car]; - [dict setObject:value forKey:symbol]; + [_bindings setObject:value forKey:symbol]; } @end |