Markdown in Nu

Wednesday October 10, 2007

Kudos to Grayson Hansard for his release today of a port of John Gruber's Markdown to Nu!

For more, see Grayson's blog and our discussion on Programming Nu.

Thanks, Grayson!

p.s. If you've been looking for an implementation of Markdown that you can easily call from Objective-C, this is it!

p.p.s and worth noting: Grayson published his first Nu code last Tuesday when he shared his port of SmartyPants to Nu. That was on Nu's second day of public life. Amazing.

Update: calling Markdown from Objective-C

I wanted to see how easy it would be to call Grayson's Markdown processor from Objective-C. Since the best way to communicate between Objective-C and Nu is through the Objective-C runtime, first I added the following class declaration to Grayson's

(class NuMarkdown is NSObject
    (+ convert:text is (Markdown text)))

Now all that we have to do is send the convert: message to the NuMarkdown class. Let's do that from a command-line program. Here's the one that I wrote for this:


@interface NuMarkdown : NSObject {}
+ (id) convert:(id) text;

int main(int argc, char *argv)
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    NSString *input = [[NSString alloc]
        initWithData:[[NSFileHandle fileHandleWithStandardInput]

    id parser = [Nu parser];
    id script = [parser parse:@"(load \"markdown\")"];
    [parser eval:script];

    Class NuMarkdown = NSClassFromString(@"NuMarkdown");
    NSString *output = [NuMarkdown convert:input];
    printf("%s", [output cStringUsingEncoding:NSUTF8StringEncoding]);

    [pool release];

Notice that although I declared the interface to NuMarkdown, that's not strictly necessary. That just keeps the compiler from generating a warning message about an unknown method.

The main thing to see is how this little program sets up Nu by creating a parser and then evaluating the (load "markdown") operator to load Grayson's Nu code. From then on, Nu is totally invisible. As far as this program is concerned, the NuMarkdown class and its convert: method are completely implemented in Objective-C. In fact, they are, because Nu is written on, with, and for Objective-C.

To run this program, compile it with:

gcc nudown.m -framework Cocoa -framework Nu -o nudown

Then run it from the command line, giving it some Markdown on standard input. You'll get formatted HTML on standard output.

That's it! Thanks to Grayson and Nu, we now have a native Objective-C Markdown processor.

What's next?