glex

A simple lexer generator for Gleam

glex is a simple lexer generator for Gleam. It is inspired by the rply lexer generator and glexer.

gleam add glex

import gleam/io
import gleam/list
import gleam/string
import glex

pub fn main() {
 // Making a lexer for a simple rung of ladder logic

 let file_type = "([A-Za-z]){1,2}"
 let file_number = "([2-9]?[0-5]?[0-5]?)?"
 let element_delimiter = "(:|/)"
 let element_number = "(\\d{1,4}|[A-Za-z]{1,4})"
 let word_delimiter = "([.|/])?"
 let word_number = "(\\d{1,4}|[A-Za-z]{1,4})?"
 let bit_delimiter = "(/)?"
 let bit_number = "(\\d{1,4}|[A-Za-z]{1,4})?"

 let address =
   string.concat([
     file_type,
     file_number,
     element_delimiter,
     element_number,
     word_delimiter,
     word_number,
     bit_delimiter,
     bit_number,
   ])

 let rung = "SOR XIC T4:0.1/DN OTE B3/0 EOR"

 let tokens =
   glex.new()
   |> glex.add_rule("SOR", "SOR")
   |> glex.add_rule("EOR", "EOR")
   |> glex.add_rule("XIC", "XIC")
   |> glex.add_rule("OTE", "OTE")
   |> glex.add_rule("ADDRESS", address)
   |> glex.add_ignore("whitespace", "\\s+")
   |> glex.build(rung)
   |> glex.lex()

 tokens
 |> list.each(io.debug)
 // #(Valid("SOR", "SOR"), Position(0))
 // #(Ignored("whitespace", " "), Position(3))
 // #(Valid("XIC", "XIC"), Position(4))
 // #(Ignored("whitespace", " "), Position(7))
 // #(Valid("ADDRESS", "T4:0.1/DN"), Position(8))
 // #(Ignored("whitespace", " "), Position(17))
 // #(Valid("OTE", "OTE"), Position(18))
 // #(Ignored("whitespace", " "), Position(21))
 // #(Valid("ADDRESS", "B3/0"), Position(22))
 // #(Ignored("whitespace", " "), Position(26))
 // #(Valid("EOR", "EOR"), Position(27))

 tokens
 |> glex.ok()
 |> io.debug
 // True

 tokens
 |> glex.valid_only()
 |> list.each(io.debug)
 // #(Valid("SOR", "SOR"), Position(0))
 // #(Valid("XIC", "XIC"), Position(4))
 // #(Valid("ADDRESS", "T4:0.1/DN"), Position(8))
 // #(Valid("OTE", "OTE"), Position(18))
 // #(Valid("ADDRESS", "B3/0"), Position(22))
 // #(Valid("EOR", "EOR"), Position(27))
}

Further documentation can be found at https://hexdocs.pm/glex.

Development

gleam run   # Run the project
gleam test  # Run the tests
gleam shell # Run an Erlang shell