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  • Are there programs that iteratively write new programs?

    - by chris
    For about a year I have been thinking about writing a program that writes programs. This would primarily be a playful exercise that might teach me some new concepts. My inspiration came from negentropy and the ability for order to emerge from chaos and new chaos to arise out of order in infinite succession. To be more specific, the program would start by writing a short random string. If the string compiles the programs will log it for later comparison. If the string does not compile the program will try to rewrite it until it does compile. As more strings (mini 'useless' programs) are logged they can be parsed for similarities and used to generate a grammar. This grammar can then be drawn on to write more strings that have a higher probability of compilation than purely random strings. This is obviously more than a little silly, but I thought it would be fun to try and grow a program like this. And as a byproduct I get a bunch of unique programs that I can visualize and call art. I'll probably write this in Ruby due to its simple syntax and dynamic compilation and then I will visualize in processing using ruby-processing. What I would like to know is: Is there a name for this type of programming? What currently exists in this field? Who are the primary contributors? BONUS! - In what ways can I procedurally assign value to output programs beyond compiles(y/n)? I may want to extend the functionality of this program to generate a program based on parameters, but I want the program to define those parameters through running the programs that compile and assigning meaning to the programs output. This question is probably more involved than reasonable for a bonus, but if you can think of a simple way to get something like this done in less than 23 lines or one hyperlink, please toss it into your response. I know that this is not quite meta-programming and from the little I know of AI and generative algorithms they are usually more goal oriented than what I am thinking. What would be optimal is a program that continually rewrites and improves itself so I don't have to ^_^

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  • How to write a bison grammer for WDI?

    - by Rizo
    I need some help in bison grammar construction. From my another question: I'm trying to make a meta-language for writing markup code (such as xml and html) wich can be directly embedded into C/C++ code. Here is a simple sample written in this language, I call it WDI (Web Development Interface): /* * Simple wdi/html sample source code */ #include <mySite> string name = "myName"; string toCapital(string str); html { head { title { mySiteTitle; } link(rel="stylesheet", href="style.css"); } body(id="default") { // Page content wrapper div(id="wrapper", class="some_class") { h1 { "Hello, " + toCapital(name) + "!"; } // Lists post ul(id="post_list") { for(post in posts) { li { a(href=post.getID()) { post.tilte; } } } } } } } Basically it is a C source with a user-friendly interface for html. As you can see the traditional tag-based style is substituted by C-like, with blocks delimited by curly braces. I need to build an interpreter to translate this code to html and posteriorly insert it into C, so that it can be compiled. The C part stays intact. Inside the wdi source it is not necessary to use prints, every return statement will be used for output (in printf function). The program's output will be clean html code. So, for example a heading 1 tag would be transformed like this: h1 { "Hello, " + toCapital(name) + "!"; } // would become: printf("<h1>Hello, %s!</h1>", toCapital(name)); My main goal is to create an interpreter to translate wdi source to html like this: tag(attributes) {content} = <tag attributes>content</tag> Secondly, html code returned by the interpreter has to be inserted into C code with printfs. Variables and functions that occur inside wdi should also be sorted in order to use them as printf parameters (the case of toCapital(name) in sample source). Here are my flex/bison files: id [a-zA-Z_]([a-zA-Z0-9_])* number [0-9]+ string \".*\" %% {id} { yylval.string = strdup(yytext); return(ID); } {number} { yylval.number = atoi(yytext); return(NUMBER); } {string} { yylval.string = strdup(yytext); return(STRING); } "(" { return(LPAREN); } ")" { return(RPAREN); } "{" { return(LBRACE); } "}" { return(RBRACE); } "=" { return(ASSIGN); } "," { return(COMMA); } ";" { return(SEMICOLON); } \n|\r|\f { /* ignore EOL */ } [ \t]+ { /* ignore whitespace */ } . { /* return(CCODE); Find C source */ } %% %start wdi %token LPAREN RPAREN LBRACE RBRACE ASSIGN COMMA SEMICOLON CCODE QUOTE %union { int number; char *string; } %token <string> ID STRING %token <number> NUMBER %% wdi : /* empty */ | blocks ; blocks : block | blocks block ; block : head SEMICOLON | head body ; head : ID | ID attributes ; attributes : LPAREN RPAREN | LPAREN attribute_list RPAREN ; attribute_list : attribute | attribute COMMA attribute_list ; attribute : key ASSIGN value ; key : ID {$$=$1} ; value : STRING {$$=$1} /*| NUMBER*/ /*| CCODE*/ ; body : LBRACE content RBRACE ; content : /* */ | blocks | STRING SEMICOLON | NUMBER SEMICOLON | CCODE ; %% I am having difficulties on defining a proper grammar for the language, specially in splitting WDI and C code . I just started learning language processing techniques so I need some orientation. Could someone correct my code or give some examples of what is the right way to solve this problem?

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  • Is it easier to write a recursive-descent parser using an EBNF or a BNF?

    - by Vivin Paliath
    I've got a BNF and EBNF for a grammar. The BNF is obviously more verbose. I have a fairly good idea as far as using the BNF to build a recursive-descent parser; there are many resources for this. I am having trouble finding resources to convert an EBNF to a recursive-descent parser. Is this because it's more difficult? I recall from my CS theory classes that we went over EBNFs, but we didn't go over converting them into a recursive-descent parser. We did go over converting BNF's into a recursive-descent parser. The reason I'm asking is because the EBNF is more compact. From looking at the EBNF's in general, I notice that terms enclosed between { and } can be converted into a while loop. Are there any other guidelines or rules?

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  • Bison: Optional tokens in a single rule.

    - by Simone Margaritelli
    Hi there .. i'm using GNU Bison 2.4.2 to write a grammar for a new language i'm working on and i have a question. When i specify a rule, let's say : statement : T_CLASS T_IDENT '{' T_CLASS_MEMBERS '}' { // create a node for the statement ... } If i have a variation on the rule, for instance statement : T_CLASS T_IDENT T_EXTENDS T_IDENT_LIST '{' T_CLASS_MEMBERS '}' { // create a node for the statement ... } Where (from flex scanner rules) : "class" return T_CLASS; "extends" return T_EXTENDS; [a-zA-Z\_][a-zA-Z0-9\_]* return T_IDENT; (and T_IDENT_LIST is a rule for comma separated identifiers). Is there any way to specify all of this only in one rule, setting somehow the "T_EXTENDS T_IDENT_LIST" as optional? I've already tried with T_CLASS T_IDENT (T_EXTENDS T_IDENT_LIST)? '{' T_CLASS_MEMBERS '}' { // create a node for the statement ... } But Bison gave me an error. Thanks

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  • "Arbitrary" context free grammars?

    - by danwroy
    Long time admirer first time inquirer :) I'm working on a program which derives a deterministic finite-state automata from a context-free grammar, and the paper I have been assigned which explains how to do this keeps referring to "arbitrary probabilistic context-free grammars" but never defines the meaning of "arbitrary" in relation to PCFGs. I assume they mean "any old PCFG" but then why not just say "any PCFG"? The term also turns up in several Wikipedia entries. At the top of the CFG page there is a reference to arbitrariness in relation to CFGs on ("clauses can be nested inside clauses arbitrarily deeply"), but doesn't make clear why someone would refer to a PCFG or subset of PCFGs as arbitrary. In case anyone is curious, the paper is Parsing and Hypergraphs by Klein and Manning (2001); I've also been reading two other papers by them related to this one (An Agenda-Based Chart Parser for Arbitrary Probabilistic Context-Free Grammars and Empirical Bounds, Theoretical Models, and the Penn Treebank) which use the term extensively but never explain it either. Thanks for your help!

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  • Best solution for language documentation.

    - by Simone Margaritelli
    I'm developing a new object oriented scripting language and the project itself is quite ready for audience now, so i'm starting to think about a serious (not as "drafty" as it is right now) way of document its grammar, functions from standard library and standard library classes. I've looked a bit around and almost every language hash its own web application for the documentation, Python uses Sphinx for instance. Which is the best PHP (don't have the time/will to install mod_who_knows_what on my server) application to accomplish this? I've used mediawiki a bit but i found its tag system a little bit hard to use in this context. Thanks for your answers.

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  • Java: how to tell if a line in a text file was supposed to be blank?

    - by defn
    I'm working on a project in which I have to read in a Grammar file (breaking it up into my data structure), with the goal of being able to generate a random "DearJohnLetter". My problem is that when reading in the .txt file, I don't know how find out whether the file was supposed to be a completely blank line or not, which is detrimental to the program. Here is an example of part of the file, How do i tell if the next line was supposed to be a blank line? (btw I'm just using a buffered reader) Thanks! <start> I have to break up with you because <reason> . But let's still <disclaimer> . <reason> <dubious-excuse> <dubious-excuse> , and also because <reason> <dubious-excuse> my <person> doesn't like you I'm in love with <another> I haven't told you this before but <harsh> I didn't have the heart to tell you this when we were going out, but <harsh> you never <romantic-with-me> with me any more you don't <romantic> any more my <someone> said you were bad news

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  • Recognizing terminals in a CFG production previously not defined as tokens.

    - by kmels
    I'm making a generator of LL(1) parsers, my input is a CoCo/R language specification. I've already got a Scanner generator for that input. Suppose I've got the following specification: COMPILER 1. CHARACTERS digit="0123456789". TOKENS number = digit{digit}. decnumber = digit{digit}"."digit{digit}. PRODUCTIONS Expression = Term{"+"Term|"-"Term}. Term = Factor{"*"Factor|"/"Factor}. Factor = ["-"](Number|"("Expression")"). Number = (number|decnumber). END 1. So, if the parser generated by this grammar receives a word "1+1", it'd be accepted i.e. a parse tree would be found. My question is, the character "+" was never defined in a token, but it appears in the non-terminal "Expression". How should my generated Scanner recognize it? It would not recognize it as a token. Is this a valid input then? Should I add this terminal in TOKENS and then consider an error routine for a Scanner for it to skip it? How does usual language specifications handle this?

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  • How to transform a production to LL(1) for a list separated by a semicolon?

    - by Subb
    Hi, I'm reading this introductory book on parsing (which is pretty good btw) and one of the exercice is to "build a parser for your favorite language." Since I don't want to die today, I thought I could do a parser for something relatively simple, ie a simplified CSS. Note: This book teach you how to right a LL(1) parser using the recursive-descent algorithm. So, as a sub-exercice, I am building the grammar from what I know of CSS. But I'm stuck on a production that I can't transform in LL(1) : //EBNF block = "{", declaration, {";", declaration}, [";"], "}" //BNF <block> =:: "{" <declaration> "}" <declaration> =:: <single-declaration> <opt-end> | <single-declaration> ";" <declaration> <opt-end> =:: "" | ";" This describe a CSS block. Valid block can have the form : { property : value } { property : value; } { property : value; property : value } { property : value; property : value; } ... The problem is with the optional ";" at the end, because it overlap with the starting character of {";", declaration}, so when my parser meet a semicolon in this context, it doesn't know what to do. The book talk about this problem, but in its example, the semicolon is obligatory, so the rule can be modified like this : block = "{", declaration, ";", {declaration, ";"}, "}" So, Is it possible to achieve what I'm trying to do using a LL(1) parser?

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  • Is there anything in .NET that allows me to define a grammar and generate a programming language?

    - by user1525474
    I have a course in which the proffesor has asked us to create a DSL for a our final project. He presented us in the first courses xText with Eclipse. This being a new course, I am still a bit fuzzy on what Domain Specific Languages means. This is my current understanding: a domain specific language is a language that is created for specific problems in software development. Examples of DSL's are PHP, SQL, JavaScript and on the opposite are languages like Java , C# , C++ , Ruby etc. Please feel free to correct me if I am wrong. What I would like to know: is there is any tool for .NET/Visual Studio that is similar to Xtext, that allows me to define a grammar and be allowed to generate a programming language based on that with an activity diagram?

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  • Lexer antlr3 token problem

    - by nioo
    Can I construct a token ENDPLUS: '+' (options (greedy = false;):.) * '+' ; being considered by the lexer only if it is preceded by a token PREwithout including in ENDPLUS? PRE: '<<' ; Thanks.

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  • GNU Flex, multiline rule

    - by Simone Margaritelli
    Hi there i have a flex rule inside my lexer definition : operators "[]"|"[]="|"[]<"|".."|"."|".="|"+"|"+="|"-"|"-="|"/"|"/="|"*"|"*="|"%"|"%="|"++"|"--"|"^"|"^="|"~"|"&"|"&="|"|"|"|="|"<<"|"<<="|">>"|"!"|"<"|">"|">="|"<="|"=="|"!="|"&&"|"||"|"~=" Is there any way to split this ruole on more lines to keep it clearer? I tried with \ just like macros but it does not seem to be accepted by flex :( PS: I don't want to split the rule in more sub-rules, but only split its regex in more lines to keep the code clearer.

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  • What makes Ometa special?

    - by Brian
    Ometa is "a new object-oriented language for pattern matching." I've encountered pattern matching in languages like Oz tools to parse grammars like Lexx/Yacc or Pyparsing before. Despite looking at example code, reading discussions, and talking to a friend, I still am not able to get a real understanding of what makes Ometa special (or at least, why some people think it is). Any explanation?

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  • Parse tree and grammars information

    - by fuzzylogikk
    Do anyone know where to find good online resources with examples how to make grammars and parsetrees? Preferebly introductary materials. Info that is n00b friendly, haven't found anything good with google myself. edit: I'm thinking about theory, not a specific parser software.

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  • Dependency parsing

    - by C.
    Hi I particularly like the transduce feature offered by agfl in their EP4IR http://www.agfl.cs.ru.nl/EP4IR/english.html The download page is here: http://www.agfl.cs.ru.nl/download.html Is there any way i can make use of this in a c# program? Do I need to convert classes to c#? Thanks :)

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  • Theory of computation - Using the pumping lemma for context free languages

    - by Tony
    I'm reviewing my notes for my course on theory of computation and I'm having trouble understanding how to complete a certain proof. Here is the question: A = {0^n 1^m 0^n | n>=1, m>=1} Prove that A is not regular. It's pretty obvious that the pumping lemma has to be used for this. So, we have |vy| = 1 |vxy| <= p (p being the pumping length, = 1) uv^ixy^iz exists in A for all i = 0 Trying to think of the correct string to choose seems a bit iffy for this. I was thinking 0^p 1^q 0^p, but I don't know if I can obscurely make a q, and since there is no bound on u, this could make things unruly.. So, how would one go about this?

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  • Why is this c# snippet legal?

    - by Sir Psycho
    Silly question, but why does the following line compile? int[] i = new int[] {1,}; As you can see, I haven't entered in the second element and left a comma there. Still compiles even though you would expect it not to.

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  • Data Quality Check - SQL Server

    - by user319384
    I am trying to find a good mechanism where I can check whether the data being entered by a group of people is grammatically correct, has correct spellings, etc, etc. I also would like to compute words per minute and accuracy. Is there any process to do this so that I do not have to re-invent the wheel? Thanks in advance.

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  • The Definition of Regular Languages

    - by AraK
    Good Day, I have tried, and burned my brain to understand the definition of Regular Languages in Discrete Mathematics and its Applications(Rosen) without reaching the goal of understanding why the definition is like that in this book. On page(789), I am rephrasing the definition: Type 3 grammars are defined as: w1 --> w2 Where w1 is a non-terminal, and w2 is of the form: w2 = aB w2 = a Where B is a non-terminal, and a is a terminal. A special case is when w1 is the starting symbol and w2 is lambda(the empty string): w1 = S S --> lambda Two questions I couldn't find an answer for. First, Why can't w2 be of the form Ba. Second, Why lambda is only allowed for the starting symbol only. The book states that, regular languages are equivalent to Finite State Automaton, and we can easily see that a we can build FSA for both cases. I took a look at other resources, and these restrictions don't exist in these resources. Thanks,

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  • Theory of computation - Using the pumping lemma for CFLs

    - by Tony
    I'm reviewing my notes for my course on theory of computation and I'm having trouble understanding how to complete a certain proof. Here is the question: A = {0^n 1^m 0^n | n>=1, m>=1} Prove that A is not regular. It's pretty obvious that the pumping lemma has to be used for this. So, we have |vy| = 1 |vxy| <= p (p being the pumping length, = 1) uv^ixy^iz exists in A for all i = 0 Trying to think of the correct string to choose seems a bit iffy for this. I was thinking 0^p 1^q 0^p, but I don't know if I can obscurely make a q, and since there is no bound on u, this could make things unruly.. So, how would one go about this?

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