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Implement destructuring pattern matching.
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| // Copyright (c) 2014 Rob Rix. All rights reserved. | ||
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| #import <Reducers/REDFilter.h> | ||
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| @interface HMRCase : NSObject | ||
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| +(id)match:(id)object withCases:(NSArray *)cases; | ||
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| +(instancetype)case:(REDPredicateBlock)predicate then:(id(^)())block; | ||
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| -(id)evaluateWithObject:(id)object; | ||
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| @end | ||
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,71 @@ | ||
| // Copyright (c) 2014 Rob Rix. All rights reserved. | ||
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| #import "HMRCase.h" | ||
| #import "HMRCombinator.h" | ||
| #import <Obstruct/apply.h> | ||
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| @implementation HMRCase { | ||
| REDPredicateBlock _predicate; | ||
| id (^_block)(); | ||
| } | ||
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| +(id)match:(id)object withCases:(NSArray *)cases { | ||
| id result; | ||
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| for (HMRCase *each in cases) { | ||
| result = [each evaluateWithObject:object]; | ||
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| if (result != nil) break; | ||
| } | ||
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| return result; | ||
| } | ||
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| l3_test(@selector(match:withCases:)) { | ||
| id object = [NSObject new]; | ||
| l3_expect([HMRCase match:object withCases:@[ [HMRCase case:REDTruePredicateBlock then:^{ return @YES; }] ]]).to.equal(@YES); | ||
| l3_expect([HMRCase match:object withCases:@[ [HMRCase case:HMRBind then:REDIdentityMapBlock] ]]).to.equal(object); | ||
| l3_expect([HMRCase match:HMRConcatenate(HMRLiteral(@"x"), HMRLiteral(@"y")) withCases:@[ [HMRCase case:HMRConcatenationPredicate(nil, HMRBind) then:REDIdentityMapBlock] ]]).to.equal(HMRLiteral(@"y")); | ||
| } | ||
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| +(instancetype)case:(REDPredicateBlock)predicate then:(id(^)())block { | ||
| return [[self alloc] initWithPredicate:predicate thenBlock:block]; | ||
| } | ||
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| -(instancetype)initWithPredicate:(REDPredicateBlock)predicate thenBlock:(id(^)())block { | ||
| NSParameterAssert(block != nil); | ||
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| if ((self = [super init])) { | ||
| _predicate = [predicate ?: REDTruePredicateBlock copy]; | ||
| _block = [block copy]; | ||
| } | ||
| return self; | ||
| } | ||
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| static _Thread_local CFMutableArrayRef variables; | ||
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| -(id)evaluateWithObject:(id)object { | ||
| CFMutableArrayRef previous = variables; | ||
| NSMutableArray *bindings = [NSMutableArray new]; | ||
| variables = (CFMutableArrayRef)CFBridgingRetain(bindings); | ||
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| id result; | ||
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| if (_predicate(object)) { | ||
| result = obstruct_apply_array(_block, bindings); | ||
| } | ||
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| variables = previous; | ||
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| return result; | ||
| } | ||
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| @end | ||
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| REDPredicateBlock const HMRBind = ^bool (id object) { | ||
| [(NSMutableArray *)CFBridgingRelease(variables) addObject:object]; | ||
| return YES; | ||
| }; |