README.md

Automa.jl

Automa is a regex-to-Julia compiler. By compiling regex to Julia code in the form of Expr objects, Automa provides facilities to create efficient and robust regex-based lexers, tokenizers and parsers using Julia's metaprogramming capabilities. You can view Automa as a regex engine that can insert arbitrary Julia code into its input matching process, which will be executed when certain parts of the regex matches an input.

Automa is designed to generate very efficient code to scan large text data, often much faster than handcrafted code.

For more information read the documentation, or read the examples below and in the examples/ directory in this repository.

Examples

Validate some text is composed only of ASCII alphanumeric characters

using Automa

generate_buffer_validator(:validate_alphanumeric, re"[a-zA-Z0-9]*") |> eval

for s in ["abc", "aU81m", "!,>"]
    println("$s is alphanumeric? $(isnothing(validate_alphanumeric(s)))")
end

Making a lexer

using Automa

tokens = [
    :identifier => re"[A-Za-z_][0-9A-Za-z_!]*",
    :lparens => re"\(",
    :rparens => re"\)",
    :comma => re",",
    :quot => re"\"",
    :space => re"[\t\f ]+",
];
@eval @enum Token errortoken $(first.(tokens)...)
make_tokenizer((errortoken, 
    [Token(i) => j for (i,j) in enumerate(last.(tokens))]
)) |> eval

collect(tokenize(Token, """(alpha, "beta15")"""))

Make a simple TSV file parser

using Automa

machine = let
    name = onexit!(onenter!(re"[^\t\r\n]+", :mark), :name)
    field = onexit!(onenter!(re"[^\t\r\n]+", :mark), :field)
    nameline = name * rep('\t' * name)
    record = onexit!(field * rep('\t' * field), :record)
    compile(nameline * re"\r?\n" * record * rep(re"\r?\n" * record) * rep(re"\r?\n"))
end

actions = Dict(
    :mark => :(pos = p),
    :name => :(push!(headers, String(data[pos:p-1]))),
    :field => quote
        n_fields += 1
        push!(fields, String(data[pos:p-1]))
    end,
    :record => quote
        n_fields == length(headers) || error("Malformed TSV")
        n_fields = 0
    end
)

@eval function parse_tsv(data)
    headers = String[]
    fields = String[]
    pos = n_fields = 0
    $(generate_code(machine, actions))
    (headers, reshape(fields, length(headers), :))
end

header, data = parse_tsv("a\tabc\n12\t13\r\nxyc\tz\n\n")