CS 11 Ocaml track: lecture 1AssignmentsRedosPassingOther administrative stuffTextbookOcaml: prosSlide 8Slide 9But wait! There's more!Ocaml: consSlide 12Ocaml: usesSlide 14Slide 15Ocaml: historySlide 17Our emphasisFunctional programmingSlide 20Slide 21Getting startedSlide 23Slide 24Slide 25Slide 26Slide 27Slide 28Stand-alone executables (1)Stand-alone executables (2)All right, then...Basic data types (1)Basic data types (2)Operatorslet expressionsDefining functions (1)Defining functions (2)Pattern matching (1)Pattern matching (2)Higher-order functions (1)Higher-order functions (2)Pattern guardsTail recursion (1)Tail recursion (2)That's all for nowCS 11 Ocaml track: lecture 1PreliminariesNeed a CS cluster accounthttp://www.cs.caltech.edu/cgi-bin/sysadmin/account_request.cgiNeed to know UNIXITS tutorial linked from track home pageTrack home page:www.cs.caltech.edu/courses/cs11/material/ocamlAssignments1st assignment is posted nowDue one week after class, midnightLate penalty: 1 mark/dayRedosRedos1st redo = 1 mark of2nd redo = 1 to 2 more marks of3rd redo = 1 to 3 more marks ofNo 4th redo! Grade - 6 mark penaltyPassingNeed average of 7/10 on labs6 labs  42/60 marksOther administrative stufSee admin web page:http://www.cs.caltech.edu/courses/cs11/material/ocaml/admin.htmlCovers how to submit labs, collaboration policy, grading, etc.TextbookIntroduction to Objective Caml by Jason Hickeydraft (don't redistribute)Ocaml: prosOcaml is a very nice language!Strong static type systemcatches lots of errors at compile timeVery expressive type systemfirst-class functionspolymorphic typesalgebraic data typesmakes it easy to build complex data typesreferences for mutable dataOcaml: prosGarbage collectionByte-code and native-code compilersVery fast!very competitive with C and C++especially if data structures are very complexInteractive interpreter for experimentingClean designCan interface with C fairly easilyOcaml: prosFully supports several diferent programming paradigms:functional programmingimperative programmingobject-oriented programmingMost natural to use as a "mostly-functional" languageSafe language: no core dumps!But wait! There's more!Type inference to get benefits of static typing without having to write out tons of declarationsVery powerful module systemincluding separate compilation of modulesParameterizable modules (functors)Simple and powerful exception handling systemPlus more experimental featuresOcaml: consVery few bad things about ocamlNative-code compiler doesn't support shared librariesthough 3rd-party tools can do thisType system sometimes too rigidObject system doesn't support "downcasting" i.e. "instanceof"Ocaml: consMessy, ambiguous syntax"Operator underloading"+ to add integers+. to add floatsFor purists: not as purely functional as e. g. HaskellSome messy aspects of type system"polymorphic references"Ocaml: usesGreat language for writing compilers!Also great for writing theorem proversRecently, Ocaml used for tasks in many other areas:simulationsfinanceoperating systemsetc.Ocaml: usesCan compete successfully with C/C++Especially whensafety is importantdata structures are very complexIn these cases, can often outperform C/C++Example: Ensemble system re-written from C  Ocaml; new version fasterOcaml: usesWhy should Ocaml give faster code in those cases?After all, C/C++ "closer to the machine"Answer:easier to tweak very complex algorithms in ways that would overwhelm C/C++ programmersand still have correct, working codeOcaml: historyOcaml is a dialect of the "ML" languageML originally the "meta-language" for a theorem-proving program called "LCF""Logic for Computable Functions"Ocaml: historyAdapted into a language called CAML by researchers in INRIA (France)"Categorical Abstract Machine Language"Newer versions have a very diferent internal structure, but kept name"Ocaml" is "Objective Caml"CAML with object-oriented extensionsPrime candidate for worst computer language name of all timeOur emphasisIn this track, we will focus on Ocaml's use as a functional programming languageWe will also cover imperative aspectsbut not OO featuresGood preparation for e.g. CS 134b (compiler course)Functional programmingWhat is a functional programming language?It's a language thattreats functions as "first-class" dataMeaning?Functions can bepassed as argumentscreated on-the-flyreturned as a result from other functionsFunctional programmingOther aspects of FP:Data should be persistentnames, once bound, do not get rebound(unless they are function arguments)mutable data structures like arrays avoided in favor of non-mutable data structures like singly-linked listsAssignment statements rarely usedExplicit loops rarely used; use recursion insteadHigher-order functions used a lotFunctional programmingLearning the syntax of Ocaml is relatively easyLearning to program in a "functional style" is much harderMain goal of track is to force you to learn to think this way(If you've taken CS 1, you already know how to think this way)Getting startedThe interactive interpreter is just called ocamlGet out of it by typing control-D (^D AKA end-of-file)When inside, can do essentially anything that could be done in a filedefine functionsdefine typesrun codeGetting startedThe "hello, world!" program (sort of):% ocaml Objective Caml version 3.08.3# Printf.printf "hello, world!\n";;hello, world!- : unit = ()^D%Getting startedThe "hello, world!" program (sort of):% ocaml Objective Caml version 3.08.3# Printf.printf "hello, world!\n";;hello, world!- : unit = ()^D%promptGetting startedThe "hello, world!" program (sort of):% ocaml Objective Caml version 3.08.3# Printf.printf "hello, world!\n";;hello, world!- : unit = ()^D%statementGetting startedThe "hello, world!" program (sort of):% ocaml Objective Caml version 3.08.3# Printf.printf "hello, world!\n";;hello, world!- : unit = ()^D%side efectGetting startedThe "hello, world!" program (sort of):% ocaml Objective Caml version 3.08.3# Printf.printf "hello, world!\n";;hello, world!- : unit = ()^D%result name, type and valueGetting startedIn interactive