chunks.m

/**
 To build (after building ReactiveCocoa):
 
 $ clang -framework Foundation \
         -framework AppKit \
         -I./ReactiveCocoa/ReactiveCocoaFramework/build/Release/include/ReactiveCocoa-Mac \
         -L./ReactiveCocoa/ReactiveCocoaFramework/build/Release \
         -lReactiveCocoa-Mac \
         -ObjC \
         -g -o main chunks.m
 */

#import <Foundation/Foundation.h>
#import "RACSequence.h"
#import "NSArray+RACSequenceAdditions.h"

@interface RACSequence (Chunk)

- (RACSequence *)recursiveChunk:(NSInteger)size;
- (RACSequence *)iterativeChunk:(NSInteger)size;

@end

@implementation RACSequence (Chunk)

- (RACSequence *)recursiveChunk:(NSInteger)size
{
    if (size <= 0 || [self head] == nil) {
        return [RACSequence empty];
    }

    RACSequence *chunk = [self take:size];
    RACSequence *rest  = [self skip:size];

    return [RACSequence sequenceWithHeadBlock:^id {
        return chunk;
    } tailBlock:^RACSequence *{
        return [rest recursiveChunk:size];
    }];
}

- (RACSequence *)iterativeChunk:(NSInteger)size
{
    if (size <= 0 || [self head] == nil) {
        return [RACSequence empty];
    }
    
    NSArray *array = [self array];
    NSMutableArray *allChunks = [NSMutableArray arrayWithCapacity:[array count] / size + 1];
    
    NSMutableArray *chunk = nil;
    NSInteger count = 0;
    
    for (id obj in array) {
        if (chunk != nil && count >= size) {
            [allChunks addObject:[chunk rac_sequence]];
            count = 0;
            chunk = nil;
        }
        if (chunk == nil) {
            chunk = [NSMutableArray arrayWithCapacity:size];
        }
        [chunk addObject:obj];
        count++;
    }
    
    if (chunk) {
        [allChunks addObject:[chunk rac_sequence]];
    }
    return [allChunks rac_sequence];
}

@end

int main (int argc, char *argv[])
{
    BOOL recursive = NO;
    
    switch (argv[1][0]) {
        case 'r':
            recursive = YES;
            break;
        case 'i':
            recursive = NO;
            break;
        default:
            fprintf(stderr, "Specify 'i' for iterative or 'r' for recursive.\n");
            return 1;
    }
    
    NSInteger const count = atoi(argv[2]);
    NSInteger const chunkSize = atoi(argv[3]);

    @autoreleasepool {
        NSMutableArray *numbers = [NSMutableArray arrayWithCapacity:count];
        for (NSInteger i = 0; i < count; i++) {
            [numbers addObject:@(i)];
        }
        
        RACSequence *sequence = [numbers rac_sequence];
        
        RACSequence *chunkedSequence;
        if (recursive) {
            chunkedSequence = [sequence recursiveChunk:chunkSize];
        } else {
            chunkedSequence = [sequence iterativeChunk:chunkSize];
        }
        
        // Evaluate the sequence by converting it to an array of arrays
        NSArray *chunkedArrays = [chunkedSequence valueForKeyPath:@"array.array"];
        NSLog(@"Number of chunks: %li", [chunkedArrays count]);
    }
}