Wednesday, March 12, 2014

Looking at a scripting language...and imagining the consequences

After thinking about the id subset and being pointed to WebScript, Brent Simmons imagines a scripting language. I have to admit I have been imagining pretty much the same language...and at some time decided to stop imagining and start building Objective-Smalltalk:

  • Peer of Objective-C: objects are Objective-C objects, methods are Objective-C methods, added to the runtime and indistinguishable from the outside. "You can subclass UIViewController, or write a category on it."
    <void>alertView:alertView clickedButtonAtIndex:<int>buttonIndex
       self newGame.
       self view setNeedsDisplay.
    The example is from the site, it was copied from an actual program. As you can see, interoperability with the C parts of Objective-C is still necessary, but not bothersome.
  • It has blocks:
       thumbs := self thumbsView subviews.
       viewsToRemove := thumbs selectWhereValueForKey:'filename' isEqual:filename.
       aView := viewsToRemove firstObject.
       UIView animateWithDuration:0.4
              animations: [ aView setAlpha: 0.0. ]
              completion: [ aView removeFromSuperview. 
                            UIView animateWithDuration: 0.2
                                   animations: [ self thumbsView layoutSubviews. ]
                                   completion: [ 3  ]. 
       url := self urlForFile:aFilename.
       NSFileManager defaultManager removeItemAtURL:url  error:nil.
       (self thumbsView afterDelay:0.4) setNeedsLayout.
    This example was also copied from an actual small educational game that was ported over from Flash.

    You also get Higher Order Messaging, Polymorpic Identifiers etc.

  • Works with the toolchain: this is a a little more tricky, but I've made some progress...part of that is an llvm based native compiler, part is tooling that enables some level of integration with Xcode, part is a separate toolset that has comparable or better capabilities.

While Objective-Smalltalk would not require shipping source code with your applications, due to the native compiler, it would certainly allow it, and in fact my own BookLightning imposition program has been shipping with part of its Objective-Smalltalk source hidden its Resources folder for about a decade or so. Go ahead, download it, crack it open and have a look! I'll wait here while you do.

Did you have a look? The part that is in Smalltalk is the distilled (but very simple) imposition algorithm shown here.

		isBackPage := (( pageNo / 2 ) intValue ) isEqual: (pageNo / 2 ).

		pages:=self pageMap objectAtIndex:pageNo.
		page1:=pages integerAtIndex:0.
		page2:=pages integerAtIndex:1.

		self drawPage:page1 andPage:page2 flipped:(self shouldFlipPage:pageNo).

	drawPage:<int>page1 andPage:<int>page2 flipped:<int>flipped
		drawingStream := self drawingStream.
		base := MPWPSMatrix matrixRotate:-90.

		drawingStream saveGraphicsState.
		flipped ifTrue: [ drawingStream concat:self flipMatrix ].
		width := self inRect x.

		self drawPage:page1 transformedBy:(base matrixTranslatedBy: (width * -2) y:0). 
		self drawPage:page2 transformedBy:(base matrixTranslatedBy: (width * -1) y:0). 
		drawingStream restoreGraphicsState.
Page imposition code

What this means is that any user of BookLightning could adapt it to suit their needs, though I am pretty sure that none have done so to this date. This is partly due to the fact that this imposition algorithm is too limited to allow for much variation, and partly due to the fact that the feature is well hidden and completely unexpected.

There are two ideas behind this:

  1. Open Source should be more about being able to tinker with well-made apps in useful ways, rather than downloading and compiling gargantuan and incomprehensible tarballs of C/C++ code.
  2. There is no hard distinction between programming and scripting. A higher level scripting/programming language would not just make developer's jobs easier, it could also enable the sort of tinkering and adaptation that Open Source should be about.
I don't think the code samples shown above are quite at the level needed to really enable tinkering, but maybe they can be a useful contribution to the discussion.


FITHIS said...

Any possibility to have it running on win32 with gnustep?

Marcel Weiher said...

Yes, this is definitely a possibility. I used to have Objective-Smalltalk running on Linux with Cocotron fairly recently, and most of the libraries used were on Windows with Cocotron and gnustep at earlier times.

I currently don't have the capacity to do this myself, but I'd be happy to support someone else.