int (^myBlock)(int) = ^(int num) { return num * multiplier; };

int d = i % 10; 
repeat(10, ^{ putc('0'+d); });


void (^block)(void);
typedef void (^vstr_t)(char *); 
typedef void (^workBlk_t)(void);

void AllLinesInFile(char *f, vstr_t block) {
    FILE *fp = fopen(f, "r"); 
    if (!fp) return; 
    char line[1024]; 
    while (fgets(line, 1024, fp))
        block(line); 
    fclose(fp);
}


@implementation NSArray (WWDC) 
- (NSArray *)map:(id (^)(id))xform {
    id result = [NSMutableArray array]; 
    for (id elem in self)
        [result addObject:xform(elem)]; 
    return result;
} 

- (NSArray *)collect:(BOOL ( ^ )(id))predicate {
    id result = [NSMutableArray array]; 
    for (id elem in self)
        if (predicate(elem)) 
            [result addObject:elem];
    return result;
}

// corner case: block literal in use with return type
id longLines = [allLines collect: ^ BOOL (id item) {
    return [item length] > 20;
}];

// corner case: block literal in use with return type
id longLines = [allLines collect: ^ BOOL* (id item) {
   return [item length] > 20;
}];

@end

// 1. block literal: ^{ ... };
// 2. block declaration: return_t (^name) (int arg1, int arg2, ...) NB: return_t is optional and name is also optional
// 3. block inline call ^ return_t (int arg) { ... }; NB: return_t is optional