All of cobra in one page
The purpose of this page is to see usage by looking at sample code, and have a link to the thorough documentation.
SORRY, WORK IN PROGRESS
Keywords in Alphabetical Order abstract adds all and any as assert base be body bool branch break callable catch char class const continue cue decimal def do dynamic each else end ensure enum event every except expect extend extern fake false finally float for from get has if ignore implements implies import in inherits inlined inout int interface internal invariant is listen lock mixin must namespace new nil nonvirtual not number objc of off old on or out override par partial pass passthrough post print private pro protected public raise ref require return same set shared sig stop struct success test this throw to to? trace true try uint use using var vari virtual where while yield
# a one line comment /# a multi-line comment multi? yes. #/
very top level keywords are the optional "namespace" and "use"
top level keywords are:
interface, class, struct, mixin
inside interface are:
def, pro, get, set
inside class are:
def, var, pro, get, set, const, test
inside def there can be:
test, require, ensure, body - or the beginning of code.
interface IAudioPacket def toWavPacket as WavPacket class WavPacket implements IAudioPacket cue init(bytes as uint8) # cue init is the syntax for constructor (ctor) base.init # it must call a base ctor. # ... etc: create the wav packet format, using the bytes def toWavPacket as WavPacket return this class Mp3Packet implements IAudioPacket var bytes as uint8 def toWavPacket as WavPacket wavBytes = Mp3Utils.decode(.bytes) # '.decode' is a shared (static) method. '.bytes' is a class variable. #methods without arguments, getters and public variables are accessed uniformly, with a '.' before their name. #local variables (inside a 'def') don't have the dot. wavpack = WavPacket(wavBytes) # instantiating a class. No need for the 'new' keyword in cobra. return wavpack
very useful for debugging are 'trace' and 'assert' }}}
# trace example def linear(a as number, x as number, b as number) as number trace a,x,b res = a * x + b trace res return res
assert accepts a boolean, with one expression per line. example: ...
contracts example: without contracts you might get surprising values, not knowing why
def gap(a as uint, b as uint) as uint test assert .gap(7,9) == 2 require 0 <= a <= 1000 # in this way it's possible to constrain the valid range of arguments for this function. 0 <= b <= 1000 # a >= b # enable this line to find the error ensure # we add ensure because we got unexpected results, and it failed. result <= 1000 # the return value is assigned to the 'result' variable, so you can test it in the 'ensure' clause body res = a - b # is something wrong with this code? (when b > a, uint handles negatives by going to uint's maxvalue) # a fix would be to check if a > b, a-b, else b-a trace res # prints out the value and variable name, along with location in code. return res
mixin VolumeSupport invariant 0 <= .volume <= 100 pro volume from var as int def decVolume .volume = Math.max(0, .volume - 1) def incVolume .volume = Math.min(100, .volume + 1)
class Radio adds VolumeSupport cue init base.init .volume = 0
class TV adds VolumeSupport cue init base.init .volume = 0
class Program def main r = Radio() assert r.volume == 0 r.incVolume assert r.volume == 1