grammar

问题 I am trying to make a flex+bison scanner and parser for Newick file format trees in order to do operations on them. The implemented grammar an explanation is based on a simplification of (labels and lengths are always of the same type, returned by flex) this example. This is esentially a parser for a file format which represents a tree with a series of (recursive) subtrees and/or leaves. The main tree will always end on ; and said tree and all subtrees within will contain a series of nodes

问题 NLTK (Natural Language Toolkit) lets you parse a FCFG grammar using nltk.FCFG.fromstring([grammar string here]). Where is the FCFG grammar format specification*? I googled it to death, but all I could find was this. *i.e. grammar language specification 回答1: From the demo: >>> from nltk import CFG >>> grammar = CFG.fromstring(""" ... S -> NP VP ... PP -> P NP ... NP -> Det N | NP PP ... VP -> V NP | VP PP ... Det -> 'a' | 'the' ... N -> 'dog' | 'cat' ... V -> 'chased' | 'sat' ... P -> 'on' |

问题 Given the following language described as: formally: (identifier operator identifier+)* in plain English: zero or more operations written as an identifier (the lvalue), then an operator, then one or more identifiers (the rvalue) An example of a sequence of operations in that language would be, given the arbitrary operator @ : A @ B C X @ Y Whitespace is not significant and it may also be written more clearly as: A @ B C X @ Y How would you parse this with a yacc-like LALR parser ? What I

问题 I am trying to build a small bison grammar, but am having an issue with part of the definition. Functions can be called with any expression legal on the right side (expression_list in the grammar) as arguments. The issue arises because on the left side, functions can be defined by assigning to them (an identifier followed by a list of identifiers - assignment_expression and identifier_list in the grammar) My question is how I can eliminate the ambiguity in my grammar, since the statements

问题 I would like to write a validator for json files that conforms to the json schema paradigm. I've been looking for a grammar that describes json schema without any luck. Do you know if there is any formal description of the json schema specifications that I can use to write a parser? Thank you. f. 回答1: The meta-schema is at http://json-schema.org/schema The semantics are defined in http://json-schema.org/latest/json-schema-validation.html 来源： https://stackoverflow.com/questions/29435810

问题 I am writing a Commodore BASIC interpreter in Prolog, and I am writing some DCGs to parse it. I have verified the DCGs below to work except for the variable one. My goal is this: for anything which isn't a boolean, integer, float, or a string, it's a variable. However, anything that I give it via phrase just results in no . bool --> [true]. bool --> [false]. integer --> [1]. % how to match nums? float --> [0.1]. string --> [Str], {atom_chars(Str, ['"' | Chars]), last(Chars, '"')}. literal -->

问题 I am writing a Commodore BASIC interpreter in Prolog, and I am writing some DCGs to parse it. I have verified the DCGs below to work except for the variable one. My goal is this: for anything which isn't a boolean, integer, float, or a string, it's a variable. However, anything that I give it via phrase just results in no . bool --> [true]. bool --> [false]. integer --> [1]. % how to match nums? float --> [0.1]. string --> [Str], {atom_chars(Str, ['"' | Chars]), last(Chars, '"')}. literal -->

问题 I am writing a Commodore BASIC interpreter in Prolog, and I am writing some DCGs to parse it. I have verified the DCGs below to work except for the variable one. My goal is this: for anything which isn't a boolean, integer, float, or a string, it's a variable. However, anything that I give it via phrase just results in no . bool --> [true]. bool --> [false]. integer --> [1]. % how to match nums? float --> [0.1]. string --> [Str], {atom_chars(Str, ['"' | Chars]), last(Chars, '"')}. literal -->

来源： https://stackoverflow.com/questions/30479367/antlr4-recover-from-error-and-continue-parsing-until-eof

来源： https://stackoverflow.com/questions/30479367/antlr4-recover-from-error-and-continue-parsing-until-eof