Category Archives: code

swift curried functions

Ran across this just now and found the comment by Pavol more interesting than curried functions. Yes Pavol! Totally. This is going to be a recurring problem for a lot of imperative programmers beginning to enter the world of functional programming through Swift. ‘Functional first’ is something I have to continually remind myself of. The original (imperative) gist went something like this:

curried1

Pavol advocates a more functional approach, without the “minutiae” of loops and temp vars:

curried2

Can we continue that train of functional thought? What if we move the separator up the chain, eliminating the function call:

curried3

That was an interim step to see if it worked. Now lets wrap it up and bring back that append function, allowing us to pass any separator:

curried6

Lastly, to make it even more compact, we can remove some syntax noise in the call to reduce:

curried7

Adding Box2D to Xcode

Grab the Box2D folder and drag it into your Xcode project.

b2d1

b2d2

Make sure copy items and the correct target are both checked.

b2d3

In the project build settings, filter by “user”.

b2d4

Under ‘User Header Search Paths’ add a . for the current directory and select recursive.

b2d5

Set ‘Always Search User Paths’ to YES.

b2d6

For the given source file, you need to change the extension to *.mm

b2d7

Doing so, changes the default type to Objective-C++.

b2d8

Finally, import Box2D and begin your journey.

b2d9

CGDataProviderCreateDirect

It’s hard to find an example using CGDataProviderCreateDirect, so here’s a quick snippet:

static unsigned int* data; // used for manipulating pixel data directly

const void * getBytePointerCallback(void *info)
{
	return (void*)data;
}

@implementation SomeView

- (void)createImage
{
    CGDataProviderDirectCallbacks callbacks;
    callbacks.version = 0;
    callbacks.getBytePointer = getBytePointerCallback;
    callbacks.releaseBytePointer = NULL;
    callbacks.getBytesAtPosition = NULL;
    callbacks.releaseInfo = NULL;
    
    float w = self.layer.frame.size.width;
    float h = self.layer.frame.size.height;
    
    w *= [UIScreen mainScreen].scale;
    h *= [UIScreen mainScreen].scale;
    
    int numComponents = 4;
    uint dataLength = w * h * numComponents;
    
    data = malloc(dataLength * sizeof(uint)); // TODO: free
    
    uint r = 255;
    uint g = 0;
    uint b = 0;
    for(int i = 0; i < dataLength; ++i)
    {
        data[i] = 255 << 24 | b << 16 | g << 8 | r;
    }
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    
    CGDataProviderRef bitmapProvider = CGDataProviderCreateDirect(data,dataLength,&callbacks);

    CGImageRef bitmap = CGImageCreate(w,
                                      h,
                                      8,    // bits per component
                                      8*numComponents,  // total bits
                                      w*numComponents,  // bytes per row
                                      colorSpace,
                                      kCGBitmapByteOrderDefault,
                                      bitmapProvider,
                                      NULL,
                                      false,
                                      kCGRenderingIntentDefault);    
    
    self.layer.contents = (__bridge id)(bitmap);
    
    CGImageRelease(bitmap);
    CGDataProviderRelease(bitmapProvider);
    CGColorSpaceRelease(colorSpace);
}

couchdb reader_acl

I installed CouchDB 1.0.1 with MacPorts 1.9.1 and quickly ran into problems:

  • The ‘attachments’ test hung in Chrome 6.0.472.55. I ran the same test in Firefox 3.6.9 and it worked.
  • The ‘reader_acl’ failed with an exception.
  • I couldn’t create an admin.

The couchdb.log certainly had errors but I couldn’t find a solution online. I tried uninstalling the port and reinstalling with no luck. Eventually I gave up and downloaded CouchDBX. Creating an admin worked but it also had problems running the Test Suite (I had to Force Quit).

Then I tried Homebrew. After installation I ran the Test Suite with 100% success and was able to create an admin! Awesome, now I’ll just add org.apache.couchdb to launchctrl…hmm it’s not under /Library/LaunchDaemons or /opt/local/Library/LaunchDaemons. After a little digging I eventually found it under /usr/local/Cellar/couchdb/1.0.1/Library/LaunchDaemons/. Only a few steps remain:

  • Copy org.apache.couchdb.plist into /Library/LaunchDaemons
  • Change the value under the UserName key to your user short name (hint: look under /Users)
  • sudo launchctl start org.apache.couchdb or you can test it for sure by restarting (shortcut key: Control-Command-Eject)

Everything now appears to be in working order.

adding FLEX_HOME and building as3-signals on a mac

Fire up a terminal:

  • cd ~/Library/SDKs
  • git clone http://github.com/robertpenner/as3-signals.git

You can find the above url on the as3-signals homepage on github. My personal pref is to put 3rd party libraries under ~/Library/SDKs

If you look inside the as3-signals dir, there is a build.xml file which requires a FLEX_HOME variable to be set. So, I downloaded the Flex 4 SDK and dropped it under /Developer/SDKs/flex_sdk_4. In the terminal, we need to set the env variable FLEX_HOME. First, lets check if you have an existing one defined. In the shell, type

  • env

You should see a list of defined variables. If you need to remove an existing FLEX_HOME, you can do so by typing

  • export -n FLEX_HOME

Otherwise, you can add a new FLEX_HOME by typing:

  • FLEX_HOME=”/Developer/SDKs/flex_sdk_4″
  • export FLEX_HOME

If you type env again FLEX_HOME is now added to the list. Now we can build as3-signals.

  • cd ~/Library/SDKs/as3-signals/
  • ant

Ant looks for a build.xml by default. Upon a successful build you’ll find a .swc in the bin folder.

Note: Setting FLEX_HOME this way will only last for 1 terminal session. If you’d like a more permanent solution, see: http://mactip.blogspot.com/2004/04/setting-environment-variables.html