Types & Bandwidth is the throughput of a communication resource, - PDF document

One-Slide Summary • A type is a (possibly infinite) set of values. Each type supports a set of valid operations . Types can be latent or manifest, static or dynamic, strong or weak. • We can change the Charme interpreter to support manifest (program visible) types. • A network is a group of three or more communicating entities. Types & • Bandwidth is the throughput of a communication resource, Types & measured in bits per second. Latency is the time delay between the moment when communication is initiated and Networking Networking the moment the first bit arrives, measured in seconds. • In circuit switching , a path through a network is reserved (high quality-of-service, used in telephones). In packet switching , each packet is routed individually (internet, postal service). #2 Administrivia Outline • Start PS8 and PS9 Now – PS9 Team Requests due Friday April 10 th • Administration • 1 st CS Department Fireside Chat • StaticCharme Typechecking – TODAY (Wednesday Apr 8) 5:30pm MEC 205 • Networking History – Worth 2 points of Extra Credit on Exam 2 • Kinga's Web Fault Research Survey • Latency, Bandwidth, Switching – http://www.cs.virginia.edu/~kld5r/webfault/ • The Internet Structured Lab in – Worth 2 points of Extra Credit on Exam 2 • Dynamic Web Sites Small Hall Today! – Plus possibly $$$ ... (bring a laptop if • 2009 Computing and Communication Scholarship for Undergraduate Women you have one) – http://www.cs.virginia.edu/ccscholarship – $1000 merit scholarship, due June 30 th #3 #4 Student Comments More Student Comments • I am displeased with the course in general. I • I am displeased that the answer to question was expecting a course that showed how eight in this problem set require a lot of computing concepts relate to the liberal arts. thinking and writing code for only one point of While that is true to some extend, this class the assignment. feels more like a straight programming class. – Irony! The goal was to make it reasonable to not DrScheme is not intuitive, and makes this do all of the problem set. course much harder than 101 and 201 without • I am displeased that I have to make a dynamic really giving more information. website, which will take a lot of time and – Managing expectations is the key to happiness! likely be our hardest assignment. – Yes, the final project will be hard. #5 #6

Even More Student Comments Displeased • I am displeased that some people are opting • 21 Course and problem sets are hard/long/frustrating not to do the problem sets. I am not a • 6 Reading quizzes computer science major and this is the first cs • 5 Two exams + final = too much work at end class I have ever taken, but I still think it is • 5 Switch languages (learning on our own) important for everyone to branch out and learn • 4 Book remains dry, confusing, and without answers new things. Although some people may say • 3 Don't know what to do for PS9 that they will never use this stuff again, you • 2 It still takes too long to get help in office hours never know. • 2 Cannot drop lowest PS grade – Currently zero students have opted out of the • 2 IDLE sucks problem sets. • 8 Other #7 #8 Changes? CPrimitiveType • Vote: class CPrimitiveType(CType): def __init__(self, s): – “Ignore all reading quiz grades. I will show my class X ( Y ): self._name = s knowledge of the material elsewhere.” means X is a subclass of Y def __str__(self): return self._name • We will add answers to the textbook next year. def isPrimitiveType(self): – By hiring students ... return True def matches(self, other): • Come talk to me and I will give you six free return other.isPrimitiveType() \ final project ideas. and self._name == other._name • You can drop the lowest PS grade. #9 #10 CProcedureType CProcedureType class CProcedureType(CType): class CProcedureType(CType): def __init__(self, args, rettype): def __init__(self, args, rettype): self._args = args self._args = args self._rettype = rettype self._rettype = rettype def __str__(self): def __str__(self): return "(" + str(self._args) + " -> " \ return "(" + str(self._args) + " -> " \ + str(self._rettype) + ")" + str(self._rettype) + ")" def isProcedureType(self): return True def isProcedureType(self): return True def getReturnType(self): return self._rettype def getReturnType(self): return self._rettype def getParameters(self): return self._args def getParameters(self): return self._args def matches(self, other): def matches(self, other): return other.isProcedureType() \ return other.isProcedureType() \ and self.getParameters().matches(other.getParameters()) \ and self.getParameters().matches(other.getParameters()) \ and self.getReturnType().matches(other.getReturnType()) and self.getReturnType().matches(other.getReturnType()) ??? #11 #12

CProductType CProductType class CProductType(CType): class CProductType(CType): def __init__(self, types): self._types = types def __init__(self, types): self._types = types def __str__(self): ... def __str__(self): ... def isProductType(self): return True def isProductType(self): return True def matches(self, other): def matches(self, other): if other.isProductType(): if other.isProductType(): st = self._types st = self._types ot = other._types ot = other._types if len(st) == len(ot): if len(st) == len(ot): for i in range(0, len(st)): for i in range(0, len(st)): ??? if not st[i].matches(ot[i]): return False if not st[i].matches(ot[i]): return False # reached end of loop ==> all matched # reached end of loop ==> all matched return True return True return False return False #13 #14 Types of Types Liberal Arts Trivia: Dance StaticCharme Charme • This closed position, ¾ time standard ballroom dance featuring gliding steps and rotations. It Manifest Latent became fashionable in Vienna in the 1780s and change grammar, represent types shocked many when it was first introduced: unlike the popular folk dances of the time, it was a couples dance that involved the leader Statically Checked Dynamically Checked clasping the follower about the waist. This gave it a dubious moral status in the eyes of typecheck expressions before eval the gentry. • Bonus: My uncle Walter goes ... #15 #16 Liberal Arts Trivia: Linguistics Adding Type Checking • This Chinese language dialect (Yuet Yu or Yue def evalLoop(): Yu) is popular in Hong Kong, Macau and initializeGlobalEnvironment() southern mainland China. It retains more tones while True: ... and consonant endings from older varieties of for expr in exprs: Chinese that have been lost to other modern typ = typecheck(expr, globalEnvironment) if typ and typ.isError(): Chinese dialects. Its rarely-used written form print "Type error:" + typ.getMessage() contains many characters not used in standard else: written Chinese. See 2 nd here: res = meval(expr, globalEnvironment) if res != None: print str(res) #17 #18