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.\" Copyright (c) 2023 Benjamin Stürz
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.Dd $Mdocdate$
.Dt LEXICGEN 1
.Os
.Sh NAME
.Nm lexicgen
.Nd lexic generator
.Sh SYNOPSIS
.Nm
.Op Fl v Ar visibility
.Op Fl p Ar package
.Op Fl o Ar output-file
.Ar input-file
.Sh DESCRIPTION
.Nm
is a clone of lex(1) for generating lexers using Lexic.
See the FORMAT section for information about the format.
.Pp
The options are as follows:
.Bl -tag -width -Ds
.It Fl v Ar visibility
Change the visibility of the lexer-internal data structures and functions. (default: private)
.It Fl p Ar package
Set a Java package for the generated class.
.It Fl o Ar output-file
Write the output to
.Ar output-file
instead of a generated path.
If
.Ar output-file
is '-', then write to the standard output.
.El
.Sh FORMAT
A valid file consists of three sections:
.Bl -bullet -compact
.It
Declarations
.It
Definitions
.It
and Code (optional)
.El

The declaration section can contain the following statements:
.Bl -tag -width -Ds
.It Sy %import Ar package
Import
.Ar package .
.It Sy %eof Ar name
Declare an end of file token called
.Ar name .

Note: Should only be specified once.
.It Sy %error Ar name
Declare an error token called
.Ar name .

Note: Should only be specified once.
.It Sy name No = Sy syntax No ;
Define a variable called
.Ar name
containing
.Ar syntax
that can be refered to from token definitions.
.El

The definition section contains token definitions.
A token definition consists of a
.Ar name
and a
.Ar syntax expression .
The name must consist of alphabetic characters.

The following syntax expressions are supported:
.Bl -tag -width -Ds
.It Sy ident
An identifier is a sequence of one or more alphabetic characters.
Match if the rule identified by
.Ar ident
matches.
.It Qq Sy string
Match if the input matches all characters of
.Ar string .
.It Bq Sy range
Match, if any of the fragments match.
If
.Ar range
starts with the
.Dq ^
character, then negate the matching result.
The range consists of fragments.
A fragment can be a single character, an escape sequence or a character range.
Only single-character escape sequences are supported.
A character range has the syntax a-b,
where a is the first character and b is the last.
.It Pq expr
Grouping.
.It expr?
Zero or one counts of
.Ar expr .
.It expr+
One or more counts of
.Ar expr .
.It expr*
Zero or more counts of
.Ar expr .
.It expr1 expr2
.Ar expr1
followed by
.Ar expr2 .
.It expr1 & expr2
Only match if both
.Ar expr1
and
.Ar expr2
match.
.It expr1 \e expr2
Match only if
.Ar expr1
matches, and
.Ar expr2
doesn't.
.It expr1 | expr2
Match if either or both of
.Ar expr1
or
.Ar expr2
match.
.El

The code sections contains any arbitrary code that will be put into the generated file.

.Sh EXAMPLES
The following code is an example of a lexicgen file:
.Bd -literal
// Declarations
%import eu.bandm.tools.lexic.*
%import java.io.IOException
%import java.io.InputStreamReader
%import java.nio.charset.StandardCharsets

// Declare an end-of-file token called EOF.
%eof EOF

// Declare an error token called Error.
%error Error

Integer = "0" | [1-9][0-9]*;
Ident = [a-zA-Z_][a-zA-Z_0-9]*;

%%
// Definitions

Whitespace	: [ \en\et\er\ef]+;
// A File can be either an integer, or an identifier.
File		: Integer | Ident;

%%
// Code

public static void main(String[] args) {
	// The construct() function is generated by lexicgen and returns a Lexer.
	var lexer = construct();

	try (var rdr = new InputStreamReader(System.in, StandardCharsets.UTF_8)) {
		TokenSource<String, TokenType> tokens = lexer
			.lex(CodePointSource.read(rdr, e -> {}))
			.removeTypes(TokenType.Whitespace);
		while (true) {
			var token = tokens.get();
			if (token.getType() == TokenType.EOF)
				break;
			System.out.println(token);
		}
	} catch (IOException e) {}
}
.Ed
.Sh EXIT STATUS
.Ex -std
.Sh SEE ALSO
.Xr lex 1
.Sh AUTHORS
.An Benjamin Stürz Aq Mt benni@stuerz.xyz