Necoro’s Blog

As probably widely known, my preferred programming language is Python. But … well … I like to try out new things. Thus I sometimes look through the interwebs to find an interesting new alternative (Note: I still want to learn (and use) Haskell…). And recently I found Cobra: In short: It has a pythonic syntax, but knows natively about unit-tests and design by contract. The latter point is the interesting one: I also wanted to try D for the same purpose, but it a) has no real open source compiler (I know of), and b) pythonic look and feel is better then C-like. Only drawback(?): It is .NET based. But well … we’ll see how this works out. Cobra itself is also designed in a way, that it can use different backends later on. (I like exchangable backends :P)

The features of Cobra:

• Static and dynamic typing
• Fast(er) execution (due to using .NET)
• Pythonic … therefore quite quick to program in
• Language level support for quality

Lets put some code here (taken from the HowTo directory :))

class Utils

	shared

		def compute(x as float, y as float) as float
			require
				x > 0
				y > 0
			ensure
				result > 0   
			body
				return x.sqrt + y.sqrt

		def normalizeName(name as String) as String
			# If a contract has only one condition, you can write it
			# on one line and skip 'body'.
			require name.trim.length
			ensure result.length <= name.length
			return Utils.capped(name.trim)

		def capped(s as String) as String
			"""
			Returns the string with the first character capitalized.
			Returns a blank string for a blank string.
			"""
			ensure
				result.length == s.length
				result.length implies result[0] == result[0].toUpper
			test
				# Unit tests can enhance contracts by showing example
				# invocations and verifying behavior.
				assert Utils.capped('chuck')=='Chuck'
				assert Utils.capped('Chuck')=='Chuck'
				assert Utils.capped('')==''
				assert Utils.capped(' foo')==' foo'
				assert Utils.capped('f')=='F'
				assert Utils.capped('1aoeu')=='1aoeu'
			body
				if s.length
					return s[0:1].toUpper + s[1:]
				else
					return s

So … let’s see where this is going to lead :). I plan to make an ebuild for the next release (the current ones do not include sourcecode) … and then the fun can start.