pratt-parser

Pratt Parser

Based on
Top Down Operator Precedence and
Douglas Crockford TDOP

``javascript
import { Parser, WhiteSpaceToken, NumberToken } from "pratt-parser";

function Value(value) {
return Object.create(null, {
value: {
value: value
}
});
}

const myGrammar = new Parser({
tokens: [WhiteSpaceToken, NumberToken],
prefix: {
"(": {
nud(grammar) {
const e = grammar.expression(0);
grammar.advance(")");
return e;
}
}
},
infix: {
")": {},
"+": {
precedence: 50,
combine: (left, right) => Value(left.value + right.value)
},
"-": {
precedence: 50,
combine: (left, right) => Value(left.value - right.value)
},
"*": {
precedence: 60,
combine: (left, right) => Value(left.value * right.value)
},
"/": {
precedence: 60,
combine: (left, right) => Value(left.value / right.value)
}
}
});

console.log(myGrammar.parse("(1 + (1 + 4 3)) (2 + 1)").value);
`

API

$3

* ParsePosition
* Properties
* Token
* Properties
* RootToken
* parse
* Parameters
* WhiteSpaceToken
* LineCommentToken
* EOFToken
* Parser
* Parameters
* error
* Parameters
* parse
* Parameters
* Tokenizer
* Parameters
* tokens
* Parameters
* error
* Parameters

ParsePosition

Type: Object

$3

* offset number
* chunk string

Token

Type: Object

$3

* type string
* precedence number
* value any

RootToken

Base object for all tokens

$3

Parses from chunk of PrasePosition and delivers next token
Modifies ParsePosition so that it points behind the detected token.

#### Parameters

* pp ParsePosition

Returns Token

WhiteSpaceToken

skip white space

LineCommentToken

skips until end of line

EOFToken

Token representing 'end of file'

Parser

Creates a grammar for later parsing

$3

* grammar any
* options Object?

$3

Forwards error to the tokenizer

#### Parameters

* args ...any

Returns Object error

$3

Parses the input and delivers the outermoost expression.

#### Parameters

* chunk string input text
* context Object object transparently passed to tokenizer

Returns Object evaluated input

Tokenizer

Creates a tokenizer for later parsing.

$3

* grammar Object definition of the grammar with operators...

$3

Delivers tokens from the input.

#### Parameters

* chunk string the input to be processed
* context Object additional info to be used by the actual token types

$3

#### Parameters

* message string
* context Object token initiating the error
* value Object?

Returns Object error

install

With npm do:

`shell
npm install pratt-parser
``

license

BSD-2-Clause