---
name: "smllex"
section: "1"
platform: "linux"
package: "smlsharp"
version: "4.1.0-1+b1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/smllex"
---

# smllex(1)

the lexical analyzer generator for SML#

## NAME

smllex - the lexical analyzer generator for SML#

## SYNOPSIS

**smllex** \[**-o** *file*\] *filename ...*

## DESCRIPTION

*SMLLex* is a lexical analyzer generator in the style of ML-Lex. It accepts input files designed for ML-Lex. Generated programs can be compiled by the SML# compiler. They are compatible to those of ML-Lex with a few exceptions.

When multiple input files are given, each input file is separately read and yields a separate program. By default, the output file name is obtained by appending *.sml* suffix to the input file name.

To compile the generated program with SML#, an interface file (*.smi* file) is needed. See **EXAMPLES** for details.

### OPTIONS

- **-o** *filename*

  Set the output file name of the first input.

## EXAMPLES

The following is a minimal example of an input file *ex.lex*:

```
type lexresult = bool option
fun eof () = NONE
%%
%structure ExampleLex
%%
"T" => (SOME true);
"F" => (SOME false);
```

By applying this file to **smllex**,

```
smllex ex.lex
```

you obtains a program named *ex.lex.sml*. To compile it, you need to create the following *ex.lex.smi* file by yourself:

```
_require "basis.smi"
structure ExampleLex =
struct
  exception LexError
  val makeLexer : (int -> string) -> unit -> bool option
end
```

When your *.lex* file has an **%arg**, directive, for example,

```
type lexresult = bool option
fun eof {inverse} = NONE
%%
%structure Example2Lex
%arg ({inverse});
%%
"T" => (SOME (if inverse then false else true));
"F" => (SOME (if inverse then true else false));
```

the generated `makeLexer` function takes an additional argument:

```
_require "basis.smi"
structure Example2Lex =
struct
  exception LexError
  val makeLexer : (int -> string) -> {inverse : bool}
                  -> unit -> bool option
end
```

## HISTORY

SMLLex is a derivative of ML-Lex, which is originally developed by Andrew W. Appel, James S. Mattson, and David R. Tarditi.

Major changes from the orginal ML-Lex includes the following:

- •

  The command line option **-o** is added.

- •

  The character position starts with 0, not 2.

- •

  The generated program does not use *Unsafe* features of SML/NJ.

## SEE ALSO

[*smlyacc*(1)](/smlyacc/1.md)\
 *A lexical analyzer generator for Standard ML*, available at https://www.smlnj.org/doc/ML-Lex/manual.html\
 *SML# Document*, available at https://www.pllab.riec.tohoku.ac.jp/smlsharp/docs/