├── .gitignore ├── Cargo.toml ├── LICENSE ├── README.md ├── src ├── codegen.rs ├── lib.rs └── parser.rs └── tests ├── basic.rs └── json.rs /.gitignore: -------------------------------------------------------------------------------- 1 | /target 2 | **/*.rs.bk 3 | Cargo.lock -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "nom-peg" 3 | version = "0.1.1" 4 | description = "A PEG parser generator built on top of nom" 5 | 6 | authors = ["Evelyn_H "] 7 | license = "GPL-3.0-or-later" 8 | repository = "https://github.com/rust-bakery/nom-peg" 9 | 10 | readme = "README.md" 11 | keywords = ["parser", "parser-combinators", "parsing", "parser-generator", "nom"] 12 | categories = ["parsing"] 13 | 14 | 15 | # edition = "2018" 16 | 17 | [lib] 18 | proc-macro = true 19 | 20 | [dependencies] 21 | nom = "^4.2.3" 22 | syn = { version = "^0.15.26", features = ["full", "extra-traits"] } 23 | quote = "^0.6.11" 24 | proc-macro2 = "^0.4.27" 25 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # PEG Grammars for Nom 2 | 3 | nom-peg is a PEG (Parsing Expression Grammar) parser generator built on top of [nom](https://github.com/Geal/nom), using a syntax that is heavily inspired by [LALRPOP](https://github.com/lalrpop/lalrpop). 4 | 5 | Grammars defined with nom-peg can freely be mixed with other nom parsers. 6 | 7 | ## Example 8 | ```rust 9 | let arithmetic = grammar! { 10 | // a grammar can have as many non-terminals as you want, and can return any type 11 | parse: i64 = "=" 12 | 13 | // alternatives are separated by `|`, 14 | // and the `=> { ... }` syntax is used to manipulate the output of the parser before returning it 15 | term: i64 = "+" => { l + r } 16 | | "-" => { l - r } 17 | | factor 18 | 19 | // the `<...>` syntax is used to capture the output of a sub-parser, 20 | // and optionally assign it to a local variable with `` 21 | factor: i64 = "*" => { l * r } 22 | | "/" => { l / r } 23 | | value 24 | 25 | value: i64 = ("0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9")+ => { result.join("").parse::().unwrap() } 26 | | "(" ")" 27 | }; 28 | 29 | // when the grammar is defined you can use any of the non-terminals as parser functions 30 | assert_eq!(arithmetic.parse("123="), Ok(("", 123 as i64))); 31 | assert_eq!(arithmetic.parse("1+1="), Ok(("", 2 as i64))); 32 | assert_eq!(arithmetic.parse("12+(3*7)="), Ok(("", 33 as i64))); 33 | ``` 34 | -------------------------------------------------------------------------------- /src/codegen.rs: -------------------------------------------------------------------------------- 1 | use proc_macro2::TokenStream; 2 | use quote::{quote, ToTokens, TokenStreamExt}; 3 | use syn::Ident; 4 | 5 | 6 | use super::parser::ParseTree; 7 | 8 | // This compiles, and might be a good way to return an anonymous stucture with methods 9 | // let a = { 10 | // struct Anon {} 11 | // impl Anon { 12 | // fn f(&self) -> u64 { 13 | // 5 14 | // } 15 | // } 16 | // Anon {} 17 | // }; 18 | // 19 | // println!("{:?}", a.f()); 20 | // 21 | // and this doesn't work, so Anon is hidden :) 22 | // let b = Anon {}; 23 | 24 | 25 | impl ToTokens for ParseTree { 26 | fn to_tokens(&self, tokens: &mut TokenStream) { 27 | // `__input` passed implicitly 28 | tokens.append_all(match self { 29 | ParseTree::DefinitionList(definitions) => { 30 | quote! { 31 | { 32 | struct PEGParser {} 33 | impl PEGParser { 34 | #( 35 | #definitions 36 | )* 37 | } 38 | PEGParser {} 39 | 40 | // struct PEGParser { 41 | // #name: Box ::nom::IResult> 42 | // } 43 | // PEGParser { 44 | // #name: Box::new(|input| { do_parse!(input, #expr >> (#block)) }) 45 | // } 46 | // |input: &str| do_parse!(input, #expr >> (#block)) 47 | } 48 | } 49 | } 50 | 51 | ParseTree::ParserDefinition(name, return_type, expr) => { 52 | let return_type = match return_type { 53 | Some(return_type) => quote! { #return_type }, 54 | None => quote! { &'input str }, 55 | }; 56 | quote! { 57 | fn #name<'input>(&self, input: &'input str) -> ::nom::IResult<&'input str, #return_type> { 58 | do_parse!(input, __ret: #expr >> (__ret)) 59 | } 60 | // named!(#name, do_parse!(#expr >> (#block))); 61 | } 62 | } 63 | 64 | ParseTree::Capture(term, _ident) => { 65 | // nothing happens here, `Capture` is just an indicator wrapper 66 | // that is used in the `Sequence` code generation 67 | quote! { 68 | #term 69 | } 70 | } 71 | 72 | ParseTree::NonTerminal(ident) => { 73 | quote! { 74 | call!(|input| self.#ident(input)) 75 | } 76 | } 77 | 78 | ParseTree::Call(func) => { 79 | // insert the input as the first argument 80 | quote! { 81 | call!(|input| #func(input)) 82 | } 83 | } 84 | 85 | ParseTree::Sequence(seq, block) => { 86 | 87 | // check for captures in the sequence 88 | let capture_map: Vec<(bool, &Option)> = seq.iter() 89 | .map(|expr| { 90 | match expr { 91 | ParseTree::Capture(_, ident) => (true, ident), 92 | _ => (false, &None), 93 | } 94 | }) 95 | .collect(); 96 | 97 | let block_prelude = if !capture_map.iter().any(|x| x.0) { 98 | // no captures, just use the original tuple 99 | quote! { let mut result = __result; } 100 | 101 | } else { 102 | // indices and names for all the named captures 103 | let (indices, idents): (Vec, Vec<&Ident>) = capture_map.iter() 104 | .enumerate() 105 | .filter_map(|x| { 106 | match x { 107 | (index, (_, Some(ident))) => Some((syn::Index::from(index), ident)), 108 | (_index, (_, &None)) => None, 109 | } 110 | }) 111 | .unzip(); 112 | 113 | // indices for the anonymous captures 114 | let anon_indices: Vec = capture_map.iter() 115 | .enumerate() 116 | .filter_map(|x| { 117 | match x { 118 | (index, (true, None)) => Some(syn::Index::from(index)), 119 | (_index, (_, _)) => None, 120 | } 121 | }) 122 | .collect(); 123 | 124 | quote! { 125 | let mut result = ( #( __result.#anon_indices ),* ); 126 | #( 127 | let mut #idents = __result.#indices; 128 | )* 129 | } 130 | }; 131 | 132 | let block = match block { 133 | Some(block) => quote! { #block }, 134 | None => quote! { result }, 135 | }; 136 | 137 | quote! { 138 | do_parse!(__result: tuple!(#(#seq),*) >> ( { #block_prelude #block } )) 139 | } 140 | } 141 | 142 | ParseTree::Empty => quote! { 143 | take!(0) 144 | }, 145 | 146 | ParseTree::Terminal(term) => { 147 | quote! { 148 | tag!(#term) 149 | } 150 | } 151 | 152 | ParseTree::Choice(choices) => { 153 | quote! { 154 | alt!(#(#choices)|*) 155 | } 156 | } 157 | 158 | ParseTree::Many0(term) => { 159 | quote! { 160 | many0!(#term) 161 | } 162 | } 163 | 164 | ParseTree::Many1(term) => { 165 | quote! { 166 | many1!(#term) 167 | } 168 | } 169 | 170 | ParseTree::Optional(term) => { 171 | quote! { 172 | opt!(#term) 173 | } 174 | } 175 | 176 | ParseTree::Peek(term) => { 177 | quote! { 178 | peek!(#term) 179 | } 180 | } 181 | 182 | ParseTree::Not(term) => { 183 | quote! { 184 | not!(#term) 185 | } 186 | } 187 | }); 188 | } 189 | } 190 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | extern crate proc_macro; 2 | extern crate proc_macro2; 3 | 4 | extern crate syn; 5 | use syn::parse_macro_input; 6 | 7 | extern crate quote; 8 | use quote::ToTokens; 9 | 10 | 11 | // PEG paper: http://bford.info/pub/lang/peg.pdf 12 | 13 | mod parser; 14 | mod codegen; 15 | 16 | // TODO: rewrite AST enum to facilitate `impl Parse` for each variant 17 | // TODO: support for using external non-terminals (i.e. other nom based parsers) 18 | // TODO: parser templates maybe? (like lalrpop) 19 | // TODO: extra functionality 20 | // - character classes `[a-zA-z]` 21 | // - any character, `.` 22 | // - repetition: exactly n times `{n}`, n or more times `{n,}`, at least n and at most m times `{n, m}` 23 | // - more regex features? 24 | // - handle named captures inside looping constucts 25 | 26 | // TODO: option to skip whitespace 27 | 28 | #[proc_macro] 29 | pub fn grammar(tokens: proc_macro::TokenStream) -> proc_macro::TokenStream { 30 | let parse_tree = parse_macro_input!(tokens as parser::ParseTree); 31 | // eprintln!("!! input: {:?}", parse_tree); 32 | 33 | parse_tree.into_token_stream().into() 34 | } 35 | -------------------------------------------------------------------------------- /src/parser.rs: -------------------------------------------------------------------------------- 1 | use syn::{ 2 | parenthesized, parse::Parse, parse::ParseStream, token::Paren, token, Block, Ident, Type, 3 | LitStr, Token, 4 | }; 5 | 6 | 7 | #[derive(Debug)] 8 | pub enum ParseTree { 9 | // list of all the non-terminals in this grammar 10 | DefinitionList(Vec), 11 | // definition of a new non-terminal 12 | ParserDefinition(Ident, Option, Box), 13 | 14 | // the sub-parser is wrapped in `<...>` or `` 15 | Capture(Box, Option), 16 | 17 | // identifier, must be a non-terminal in this grammar 18 | NonTerminal(Ident), 19 | // call to external parser 20 | Call(Ident), 21 | // sequence of sub-parsers, with optional action code at the end 22 | Sequence(Vec, Option), 23 | // terminal that consumes no input, equivalend to `""` 24 | Empty, 25 | // string literal 26 | Terminal(String), 27 | // ordered list of alternative sub-parsers 28 | Choice(Vec), 29 | // Repetition: 0 or more times 30 | Many0(Box), 31 | // Repetition: 1 or more times 32 | Many1(Box), 33 | // makes the sub-parser optional 34 | Optional(Box), 35 | // evaluates the sub-parser without consuming input 36 | Peek(Box), 37 | // negates the result of the sub-parser 38 | Not(Box), 39 | } 40 | 41 | 42 | enum Prefix { 43 | Peek, 44 | Not, 45 | } 46 | 47 | enum Postfix { 48 | Optional, 49 | Many0, 50 | Many1, 51 | } 52 | 53 | fn parse_prefix(input: ParseStream) -> Option { 54 | let lookahead = input.lookahead1(); 55 | if lookahead.peek(Token![&]) { 56 | // Peek 57 | input.parse::().unwrap(); // just skip past this 58 | Some(Prefix::Peek) 59 | } else if lookahead.peek(Token![!]) { 60 | // Not 61 | input.parse::().unwrap(); // just skip past this 62 | Some(Prefix::Not) 63 | } else { 64 | // No prefix found 65 | None 66 | } 67 | } 68 | 69 | fn parse_postfix(input: ParseStream) -> Option { 70 | let lookahead = input.lookahead1(); 71 | if lookahead.peek(Token![?]) { 72 | // Optional 73 | input.parse::().unwrap(); // just skip past this 74 | Some(Postfix::Optional) 75 | } else if lookahead.peek(Token![*]) { 76 | // Many0 77 | input.parse::().unwrap(); // just skip past this 78 | Some(Postfix::Many0) 79 | } else if lookahead.peek(Token![+]) { 80 | // Many1 81 | input.parse::().unwrap(); // just skip past this 82 | Some(Postfix::Many1) 83 | } else { 84 | // No postfix found 85 | None 86 | } 87 | } 88 | 89 | fn parse_element(input: ParseStream) -> syn::Result { 90 | let prefix = parse_prefix(input); 91 | 92 | let lookahead = input.lookahead1(); 93 | 94 | let mut parsed = if lookahead.peek(Ident) { 95 | // if there's an '=' sign following it's the start of a new definition 96 | if parse_definition(&input.fork()).is_ok() { 97 | // if (input.peek2(Token![=]) && !input.peek2(Token![=>])) || input.peek2(Token![:]) { 98 | Err(input.error("Reached start of new definition.")) 99 | } else { 100 | // Non-Terminal / Indentifier 101 | Ok(ParseTree::NonTerminal(input.parse::()?)) 102 | } 103 | } else if lookahead.peek(Token![::]) { 104 | // external function call 105 | input.parse::()?; 106 | Ok(ParseTree::Call(input.parse::()?)) 107 | } else if lookahead.peek(LitStr) { 108 | // Terminal 109 | Ok(ParseTree::Terminal(input.parse::()?.value())) 110 | } else if lookahead.peek(Paren) { 111 | // Grouping 112 | // Get content of parens 113 | let content; 114 | parenthesized!(content in input); 115 | // and parse the content 116 | // Ok(ParseTree::Grouping(Box::new(content.parse::()?))) 117 | Ok(parse_expression(&content)?) 118 | } else if lookahead.peek(Token![<]) { 119 | // Capture 120 | // token::Lt is Token![<], but that messed up my syntax highlighting 121 | input.parse::()?; // just skip past this 122 | 123 | let ident = if input.peek(Ident) && input.peek2(Token![:]) { 124 | // identifier 125 | let i = Some(input.parse::()?); 126 | // and then a colon 127 | input.parse::()?; // just skip past this 128 | i 129 | } else { 130 | None 131 | }; 132 | 133 | let term = parse_element(&input)?; 134 | input.parse::()?; // just skip past this 135 | 136 | Ok(ParseTree::Capture(Box::new(term), ident)) 137 | } else { 138 | Err(lookahead.error()) 139 | }; 140 | 141 | let postfix = parse_postfix(input); 142 | 143 | // process postfix 144 | parsed = parsed.and_then(|p| { 145 | Ok(match postfix { 146 | Some(Postfix::Optional) => ParseTree::Optional(Box::new(p)), 147 | Some(Postfix::Many0) => ParseTree::Many0(Box::new(p)), 148 | Some(Postfix::Many1) => ParseTree::Many1(Box::new(p)), 149 | None => p, 150 | }) 151 | }); 152 | 153 | // process prefix 154 | parsed.and_then(|p| { 155 | Ok(match prefix { 156 | Some(Prefix::Peek) => ParseTree::Peek(Box::new(p)), 157 | Some(Prefix::Not) => ParseTree::Not(Box::new(p)), 158 | None => p, 159 | }) 160 | }) 161 | } 162 | 163 | fn parse_sequence(input: ParseStream) -> syn::Result { 164 | let mut expressions: Vec = Vec::with_capacity(4); 165 | 166 | while !input.is_empty() { 167 | match parse_element(input) { 168 | Ok(e) => expressions.push(e), 169 | Err(_) => break, 170 | } 171 | } 172 | 173 | if expressions.len() == 0 { 174 | return Err(input.error("Need at least one element in a sequence")) 175 | } 176 | 177 | // let seq = match expressions.len() { 178 | // 0 => Ok(ParseTree::Empty), 179 | // 1 => Ok(expressions.remove(0)), 180 | // _ => Ok(ParseTree::Sequence(expressions)), 181 | // }; 182 | 183 | // Parse action code 184 | let block = if input.peek(Token![=>]) { 185 | // need a '=>', otherwise we don't have any action code 186 | input.parse::]>()?; // just skip past this 187 | Some(input.parse::()?) 188 | } else { 189 | None 190 | }; 191 | 192 | Ok(ParseTree::Sequence(expressions, block)) 193 | } 194 | 195 | fn parse_expression(input: ParseStream) -> syn::Result { 196 | let mut expressions: Vec = Vec::with_capacity(4); 197 | 198 | expressions.push(parse_sequence(input)?); 199 | while !input.is_empty() && input.peek(Token![|]) { 200 | input.parse::()?; // just skip past this 201 | expressions.push(parse_sequence(input)?); 202 | } 203 | 204 | match expressions.len() { 205 | 0 => Ok(ParseTree::Empty), 206 | 1 => Ok(expressions.remove(0)), 207 | _ => Ok(ParseTree::Choice(expressions)), 208 | } 209 | } 210 | 211 | fn parse_definition(input: ParseStream) -> syn::Result { 212 | // parse name 213 | let name = input.parse::()?; 214 | 215 | // optionally parse a type 216 | let return_type = if input.peek(Token![:]) { 217 | input.parse::()?; // just skip past this 218 | Some(input.parse::()?) 219 | } else { 220 | None 221 | }; 222 | 223 | // then an equals sign 224 | input.parse::()?; // just skip past this 225 | 226 | // parse expression 227 | let expression = parse_expression(input)?; 228 | 229 | // Final ast node 230 | Ok(ParseTree::ParserDefinition(name, return_type, Box::new(expression))) 231 | } 232 | 233 | impl Parse for ParseTree { 234 | fn parse(input: ParseStream) -> syn::Result { 235 | let mut definitions: Vec = Vec::with_capacity(4); 236 | 237 | definitions.push(parse_definition(input)?); 238 | while !input.is_empty() { 239 | definitions.push(parse_definition(input)?); 240 | } 241 | Ok(ParseTree::DefinitionList(definitions)) 242 | } 243 | } 244 | -------------------------------------------------------------------------------- /tests/basic.rs: -------------------------------------------------------------------------------- 1 | #![feature(proc_macro_hygiene)] 2 | 3 | #[macro_use] 4 | extern crate nom; 5 | extern crate nom_peg; 6 | use nom_peg::grammar; 7 | 8 | #[test] 9 | fn peg_test() { 10 | // fn execute_op(left: i64, op: &str, right: i64) -> i64 { 11 | // match op { 12 | // "+" => left + right, 13 | // "-" => left - right, 14 | // "*" => left * right, 15 | // "/" => left / right, 16 | // _ => unreachable!() 17 | // } 18 | // } 19 | // 20 | // let arithmetic = grammar! { 21 | // parse: i64 = expr "=" => { result.0 } 22 | // 23 | // expr: i64 = product (("+" | "-") product)* => { 24 | // result.1.iter().fold(result.0, |a, i| execute_op(a, i.0, i.1)) 25 | // } 26 | // 27 | // product: i64 = value (("*" | "/") value)* => { 28 | // result.1.iter().fold(result.0, |a, i| execute_op(a, i.0, i.1)) 29 | // } 30 | // 31 | // value: i64 = ("0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9")+ => { result.join("").parse::().unwrap() } 32 | // | "(" expr ")" => { result.1 } 33 | // }; 34 | 35 | // this grammar is right-associative, which might give different results for integer division 36 | // eg. 3*7/2 should equal 10, but here it's executed as 3*(7/2), which equals 9 instead. 37 | let arithmetic = grammar! { 38 | parse: i64 = "=" 39 | 40 | expr: i64 = "+" => { l + r } 41 | | "-" => { l - r } 42 | | product 43 | 44 | product: i64 = "*" => { l * r } 45 | | "/" => { l / r } 46 | | value 47 | 48 | value: i64 = ("0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9")+ => { result.join("").parse::().unwrap() } 49 | | "(" ")" 50 | }; 51 | 52 | // I realised this grammar actually isn't correct, 53 | // e.g. it doesn't parse: "3*7/2" 54 | // let arithmetic = grammar! { 55 | // parse: i64 = expr "=" => { result.0 } 56 | // 57 | // expr: i64 = product ("+" product => { result.1 })* => { result.1.iter().fold(result.0, |a, i| a + i) } 58 | // | product ("-" product => { result.1 })* => { result.1.iter().fold(result.0, |a, i| a + i) } 59 | // 60 | // product: i64 = value ("*" value => { result.1 })* => { result.1.iter().fold(result.0, |a, i| a * i) } 61 | // | value ("/" value => { result.1 })* => { result.1.iter().fold(result.0, |a, i| a / i) } 62 | // 63 | // value: i64 = ("0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9")+ => { result.join("").parse::().unwrap() } 64 | // | "(" expr ")" => { result.1 } 65 | // }; 66 | 67 | assert_eq!(arithmetic.parse("123="), Ok(("", 123 as i64))); 68 | assert_eq!(arithmetic.parse("1+1="), Ok(("", 2 as i64))); 69 | assert_eq!(arithmetic.parse("12+(3*7)="), Ok(("", 33 as i64))); 70 | // assert_eq!(arithmetic.parse("3*7/2="), Ok(("", 10 as i64))); // left-associative 71 | assert_eq!(arithmetic.parse("3*7/2="), Ok(("", 9 as i64))); // right-associative 72 | 73 | let parser = grammar! { 74 | p = &"a"* "a"* => { "yay" } 75 | q: String = a ("b" | "c") => { result.0 } 76 | | a "d" => { result.0 } 77 | // a = "a"* => { result[0] } 78 | a: String = "a"* => { result.join("") } 79 | // a: Vec<&'input str> = "a"* => { result } 80 | }; 81 | 82 | assert_eq!(parser.p("abc"), Ok(("bc", "yay"))); 83 | assert_eq!(parser.p("aaaaaaab"), Ok(("b", "yay"))); 84 | 85 | assert_eq!(parser.q("aaabcc"), Ok(("cc", String::from("aaa")))); 86 | assert_eq!(parser.q("aac"), Ok(("", String::from("aa")))); 87 | } 88 | -------------------------------------------------------------------------------- /tests/json.rs: -------------------------------------------------------------------------------- 1 | #![feature(proc_macro_hygiene)] 2 | 3 | #[macro_use] 4 | extern crate nom; 5 | extern crate nom_peg; 6 | 7 | use nom::{alphanumeric, recognize_float}; 8 | use nom_peg::grammar; 9 | 10 | use std::collections::HashMap; 11 | 12 | #[derive(Debug, PartialEq)] 13 | pub enum JsonValue { 14 | Str(String), 15 | Boolean(bool), 16 | Num(f32), 17 | Array(Vec), 18 | Object(HashMap), 19 | } 20 | 21 | 22 | #[test] 23 | fn peg_json_test() { 24 | 25 | let json = grammar! { 26 | parse: JsonValue = "=" 27 | 28 | num: f32 = ::recognize_float => { result.parse::().unwrap() } 29 | 30 | string: &'input str = "\"" <::alphanumeric> "\"" 31 | 32 | boolean: bool = "false" => { false } 33 | | "true" => { true } 34 | 35 | array: Vec = "[" ",")*> "]" => { list.push(last); list } 36 | 37 | key_value: (&'input str, JsonValue) = ":" 38 | 39 | hash: HashMap = "{" ",")*> "}" 40 | => { 41 | list.push(last); 42 | list.into_iter() 43 | .map(|(k, v)| (String::from(k), v)) 44 | .collect() 45 | } 46 | 47 | value: JsonValue = hash => { JsonValue::Object(result) } 48 | | array => { JsonValue::Array(result) } 49 | | string => { JsonValue::Str(String::from(result)) } 50 | | num => { JsonValue::Num(result) } 51 | | boolean => { JsonValue::Boolean(result) } 52 | }; 53 | 54 | let data = "{\"a\":42.3,\"b\":[\"x\",\"y\",12],\"c\":{\"hello\":\"world\"}}="; 55 | println!("{:?}", json.parse(data)); 56 | assert!(json.parse(data).is_ok()); 57 | 58 | // assert_eq!(json.parse(data), Ok(("", JsonValue::Num(0.0)))); 59 | } 60 | --------------------------------------------------------------------------------