OaxacaHom is Yet Another HigherOrderMessaging implementation. It is available at:

http://svn.smallcultfollowing.com/main/oaxaca2/oaxaca2/HOM/

It’s main claim to fame is that it uses macros to avoid the problems with BOOL return values, while preserving the portability across platforms offered by the NSInvocation interface. It is written by NikoMatsakis and released with the MIT license.

Some examples of how to use it follow:

BOOL b = OxExists(array, hasPrefix:@”a”); // Any items in array which return YES to hasPrefix:@”a”? BOOL b = OxForAll(array, hasPrefix:@”a”); // All items in array return YES to hasPrefix:@”a”? NSArray *a = OxMap(array, hasPrefix:@”a”); // from list of strings to list of boolean NSNumbers NSArray *a = OxFilter(array, hasPrefix:@”a”); // only those strings that begin with @”a” OxPerform(array, doSomething);

You can also perform repeated operations efficiently:

OxHom *hom = [OxHom homWithContentsOf:array]; hom filter] hasPrefix:@”a”]; // only strings with prefix “a” remaining [[hom map] length]; // now just the lengths of those strings [[hom filter] boolValue]; // now only non-zero lengths return hom.array; // return final result (an [[NSMutableArray)

Some other features:

• Transparently wraps numbers in NSNumber.
• Liberally licensed.
• Supports many operators and uses more functional names than the Smalltalk equivalents. Much as I love Smalltalk, I can never remember which is select and which is collect. Of course, those names are easily changed if you prefer Smalltalk style or something else.
• Small and self-contained: easy to include in your own projects.

I wrote it mainly because I wanted to tinker around with the runtime and explore the HOM idea. It’s not extensively tested, so user beware. I am using it in my own projects without problems, however.