grammar

问题 I'm fairly new to NLTK and Python. I've been creating sentence parses using the toy grammars given in the examples but I would like to know if it's possible to use a grammar learned from a portion of the Penn Treebank, say, as opposed to just writing my own or using the toy grammars? (I'm using Python 2.7 on Mac) Many thanks 回答1: If you want a grammar that precisely captures the Penn Treebank sample that comes with NLTK, you can do this, assuming you've downloaded the Treebank data for NLTK

问题 How to define a grammar (context-free) for a new programming language (imperative programming language) that you want to design from scratch. In other words: How do you proceed when you want to create a new programming language from scratch. 回答1: One step at a time. No seriously, start with expressions and operators, work upwards to statements, then to functions/classes etc. Keep a list of what punctuation is used for what. In parallel define syntax for referring to variables, arrays, hashes,

问题 I have lexer rules in Antlr3 as: HYPHEN : '-'; TOKEN : HYPHEN CHARS; CHARS : 'a' ..'z'; Parser rule is as: exp : CHARS | some complex expression; parser_rule : exp HYPHEN exp; If I try to match 'abc-abc' with parser_rule, It fails. Because lexer creates TOKEN for HYPHEN exp. How can I match it correctly with parser_rule. 回答1: In ANTLR lexer, the lexer rule that can match the longest sub-sequence of input is used. So your input abc-abc will be tokenized as CHARS("abc") TOKEN("-abc") and

问题 I have a Hello.g4 grammar file with a grammar definition: definition : wordsWithPunctuation ; words : (WORD)+ ; wordsWithPunctuation : word ( word | punctuation word | word punctuation | '(' wordsWithPunctuation ')' | '"' wordsWithPunctuation '"' )* ; NUMBER : [0-9]+ ; word : WORD ; WORD : [A-Za-z-]+ ; punctuation : PUNCTUATION ; PUNCTUATION : (','|'!'|'?'|'\''|':'|'.') ; WS : [ \t\r\n]+ -> skip ; // skip spaces, tabs, newlines Now, if I am trying to build a parse tree from the following

问题 I'm attempting to eliminate left recursion from a CFG by eliminating indirect recursion then direct recursion as this algorithm shows. I'll be using this grammar: A = A a | A B C | B C | D D When i = 1 , and j = 1 we are looking at replacing all productions of the form A -> A r with: A -> δ 1 γ | δ 2 γ | .. | δ k γ So when I look at A -> A a which matches, i should replace it with A -> A a a | A B C a a | B C a | D D a which im sure is wrong Can anyone point me in the right direction for how

问题 I'm very new in the ANTLR world and I'm trying to figure out how can I use this parsing tool to interpret a set of "noisy" string. What I would like to achieve is the following. let's take for example this phrase : It's 10PM and the Lazy CAT is currently SLEEPING heavily on the SOFA in front of the TV What I would like to extract is CAT , SLEEPING and SOFA and have a grammar that match easily the following pattern : SUBJECT - VERB - INDIRECT OBJECT... where I could define VERB : 'SLEEPING' |

问题 I'm trying to combine both the result of a semantic and a dictation request in the semantic value of a SRGS document. For example, I would say "Search potato" and the output would be something like out="Search Potato" where Potato is a random word spoken by the user. I tought about using the garbage special rule, but it doesn't seem to work. So far that's what I have : <rule id="rule1" scope="public"> <one-of> <item xml:lang="en-us">Search</item> <item>Cherche</item> </one-of> <tag>out

问题 I have the following simple expression parser: expr(+(T,E))-->term(T),"+",expr(E). expr(T)-->term(T). term(*(F,T))-->factor(F),"*",term(T). term(F)-->factor(F). factor(N)-->nat(N). factor(E)-->"(",expr(E),")". nat(0)-->"0". nat(1)-->"1". nat(2)-->"2". nat(3)-->"3". nat(4)-->"4". nat(5)-->"5". nat(6)-->"6". nat(7)-->"7". nat(8)-->"8". nat(9)-->"9". However this only supports 1-digit numbers. How can I parse numbers with multiple digits in this case? 回答1: Use accumulator variables, and pass

问题 This question is inspired by Is sizeof(void()) a legal expression? but with an important difference as explained below. The expression in question is: sizeof( int() ) In the C++ grammar there appears: unary-expression: sizeof unary-expression sizeof ( type-id ) however, ( int() ) can match both of these cases with different meanings: As a unary-expression , it is a value-initialized int prvalue, surrounded in redundant parentheses As a type-id , it is the type of a function with no parameters

问题 I am starting to write BibTeX parser. The first thing I would like to do is to parse a braced item. A braced item could be an author field or a title for example. There might be nested braces within the field. The following code does not handle nested braces: use v6; my $str = q:to/END/; author={Belayneh, M. and Geiger, S. and Matth{\"{a}}i, S.K.}, END $str .= chomp; grammar ExtractBraced { rule TOP { 'author=' <braced-item> .* } rule braced-item { '{' <-[}]>* '}' } } ExtractBraced.parse(