Parser {tangram}

The parser class for generating abstract syntax trees for given table formulas.

Description

The parser class for generating abstract syntax trees for given table formulas.

The parser class for generating abstract syntax trees for given table formulas.

Format

R6Class object.

References

Aho, A. V., Lam, M. S., Sethi, R., and Ullman, J. D. (2006) Compilers: Principles, Techniques, and Tools, 2nd edition. Addison Wesley.

Public fields

input

Storage for input string of a formula

pos

The current parsing position

len

The length of the input

Methods

Public methods

• Parser$new()

• Parser$expect()

• Parser$peek()

• Parser$eat_whitespace()

• Parser$next_token()

• Parser$format()

• Parser$r_expression()

• Parser$factor()

• Parser$term()

• Parser$expression()

• Parser$table_formula()

• Parser$run()

• Parser$clone()

Method new()

Create a parser

Usage

Parser$new()

Method expect()

Specify expectation of next token from lexer

Usage

Parser$expect(id)

Arguments

id

The token id expected in stream, otherwise it's an error

Method peek()

Peek at the next token from parser

Usage

Parser$peek()

Method eat_whitespace()

Remove white space to find start of next token

Usage

Parser$eat_whitespace()

Method next_token()

Returns next lexical token

Usage

Parser$next_token()

Method format()

Return format string as token from lexical stream

Usage

Parser$format()

Method r_expression()

Return R expression as token from lexical stream

Usage

Parser$r_expression()

Method factor()

Return next factor as token.

Usage

Parser$factor()

Method term()

Parse and return next term in stream

Usage

Parser$term()

Method expression()

Parse and return next expression in stream

Usage

Parser$expression()

Method table_formula()

Parse and return table formula from stream

Usage

Parser$table_formula()

Method run()

Run the parser

Usage

Parser$run(x)

Arguments

x

(character,formula) The table specification to parse

Method clone()

The objects of this class are cloneable with this method.

Usage

Parser$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

Parser$new()$run("col1 + col2 + col3 ~ drug*age+spiders")