Introduction. ML-Modules & ML-Lex. Agenda. Overview. The Assignment. The Assignment. ML-Modules & ML-Lex 1. Erik (Happi) Johansson.

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1 ML-Modules & ML-Lex Erik (Happi) Johansson Room: Introduction z The lessons will be concerned with the assignment. z Today we will talk about some ML concepts you will need, and the first part of the assignment. Aga z The Assignment z Advanced ML (SML-NJ) Records Exception handling Module system Standalone execution Makefiles z ML-Lex Overview z The assignment has four parts Lexical analysis Syntactic analysis Semantic analysis Bar Native code generation z The final compiler should be written in ML ML Unix Lexical analysis Compiler (In ML) SPIM MIPS Syntactic analysis Semantic analysis Native Code The Assignment z Goal A complete compiler from source code to native machine code. z Motivation Give understanding of all parts of a compiler. Give understanding of program execution. Give experience in programming. z Rules Groups of 2 persons. Absolute deadlines. The Assignment z Compile the language Bar Bar is a call by value, imperative language with static lexical scoping. Bar is strongly statically typed with explicit typing of declarations. Bar has integers, floats, truthvalues (booleans), and arrays of these types. Bar has basic control structures, functions and procedures. Bar has destructiv updates of variabels. z Compile to MIPS ML-Modules & ML-Lex 1

2 The language Bar (example) [int:1] a; Declare a global array (a) of one integer + The function foo(b) takes an array of integer and returns a boolean. + function foo([int] b):bool begin b[0] = 1; Assign the value 1 to the first element in b. Note that arrays are passed by reference, so the array used in the call to foo will be updated. return true; Return the boolean true. + The main body of the program. Calls the function foo and deping on the return value either prints the first element in the global array a, or the boolean false. + begin if foo(a) then print a[0]; else print false; Bar Grammar 1 (of 4) Bar Grammar 2 (of 4) Bar Grammar 3 (of 4) Bar Grammar 4 (of 4) Advanced ML z Records z Exception handling z Module system z Standalone execution z Makefiles ML-Modules & ML-Lex 2

3 Records Just like tuples with named elements. - val car = {make = "SAAB", built = 2000}; val car = {built=2000,make="saab"} : {built:int, make:string} - #built car; val it = 2000 : int - fun uppgrade{make,built = year} = {make=make, built=year+1}; val uppgrade = fn : {built:int, make:'a} -> {built:int, make:'a} - uppgrade car; val it = {built=2001,make="saab"} : {built:int, make:string} Exception handling exception Error of int * string; fun f v = (case v of 1 => 42 _ => raise Error (1,"not 1") ) handle Error (no, s) => (print s; print \n ; no); - f 2; not 1 val it = 1 : int Module system z The basis for the ML module system is the structure. z You have probably seen and used structures several times. Ex. TextIO.print TextIO is a structure that defines the function print. Structures z A structure is defined as structure NAME = struct DEFINITIONS z Ex structure foo = struct type t = string say = fn x => TextIO.print x Signatures z Signatures gives the type of a structure. z They are declared as: signature NAME = sig DECLARATIONS z Ex signature bar = sig type t val say : t -> unit Ascription z To say that a structure implements a signature. z Can be transparent ( : ) or opaque ( :> ). structure foo:bar = struct type t = string say = fn x => TextIO.print x ML-Modules & ML-Lex 3

4 Standalone Execution z Created by saving the state of the run-time system to a file. z A start function of type string * string list -> OS.Process.status is needed. z The state is saved by calling SMLofNJ.exportFn with a tuple (FileName, StartFunction) z The program is then executed by: Args Example of standalone execution - fun start (path, args) = (print (path ^ "\n"); map (fn x => print x) args; OS.Process.success); - SMLofNJ.exportFn ("testit", start); > 42 /it/sw/ml/bin/sml 42 Makefiles z Use the ML - Compilation Manager z Create a file called VRXUFHVFP z List the source files of your project in this file preceded by the keywords *URXS LV z When you have a sources.cm file you can just type: &0PDNH in the ML-shell to compile all files as necessary. Example of sources.cm Group is testlexer.sml errormsg.sml tokens.sig tokens.sml lexer.lex smlnj-lib.cm z The last file is needed to get the SML standard libraries. The compilation manager should find this file by it self. z The compilation manager recognizes.lex files and executes ml-lex. ML Lex z ML lex takes a file with rules describing tokens of a language and compiles them into a program that can turn a string in the language to the tokens of the string. z We will look at The lexer file.lex How to run ML-Lex How to call the lexer The lexer file (.lex) User declarations (ML-code) %% ML-LEX definitions (abreviations) %% Rules ML-Modules & ML-Lex 4

5 Declarations (.lex) z Two required The function eof fun eof() = Tokens.EOF The type of lexresult type lexresult = Tokens.tokens z Any other help function you need. ML-Lex definitions (.lex) z Give start states %s SkipComment; z Give names to regular expressions digit=[0-9]; int={digit}+; exp=((e E)"-"?{int}); floats={int}"."{int}{exp}?; ML-Lex Rules (.lex) Regexp action <STATE>Regexp action (action should be of type lexresult.) {floats} => (case Real.fromString yytext of NONE => ErrorMsg.impossible ("Cannot convert" ^ yytext) SOME f => Tokens.FLOAT(f, yypos, yypos+ String.size yytext)); To run ML-Lex Typing ml-lex lexer.lex at the unix prompt, should give a file lexer.lex.sml (If your path contains /it/sw/ml/bin/ml-lex) To use the lexer in a program z The file *.lex.sml defines a ML structure Mlex, which contains the function makelexer. z This function should be called with a function of the type int -> string z This second function should read up to N characters from the in-stream. z The function makelexer returns a function that returns the next token each time it is called. Example of how to use the lexer in a program fun makeget stream = let fun get (_:int) = TextIO.input stream in get fun tokenize (lexer) = let val token = lexer() in (case token of Tokens.EOF(_) => () => (print (Tokens.toString token); tokenize(lexer))) fun do_it (s:string, slist:string list) = let val lexer = Mlex.makeLexer (make_get TextIO.stdIn) in (tokenize(lexer); OS.Process.success) ML-Modules & ML-Lex 5

6 Where to Get More Information z The assignment page: z A lexical analyzer generator for Standard ML: z Standard ML of New Jersey User's Guide: z CM -- A Compilation Manager for SML/NJ -- User Manual: ML-Modules & ML-Lex 6