Chapter 10. Other Haskell utility programs

Table of Contents

10.1. Ctags and Etags for Haskell: hasktags
10.1.1. Using tags with your editor
10.2. “Yacc for Haskell”: happy
10.3. Writing Haskell interfaces to C code: hsc2hs
10.3.1. command line syntax
10.3.2. Input syntax
10.3.3. Custom constructs

This section describes other program(s) which we distribute, that help with the Great Haskell Programming Task.

10.1. Ctags and Etags for Haskell: hasktags

hasktags is a very simple Haskell program that produces ctags "tags" and etags "TAGS" files for Haskell programs.

When loaded into an editor such an NEdit, Vim, or Emacs, this allows one to easily navigate around a multi-file program, finding definitions of functions, types, and constructors.

Invocation Syntax:

hasktags files

This will read all the files listed in files and produce a ctags "tags" file and an etags "TAGS" file in the current directory.

Example usage

find -name \*.\*hs | xargs hasktags

This will find all haskell source files in the current directory and below, and create tags files indexing them in the current directory.

hasktags is a simple program that uses simple parsing rules to find definitions of functions, constructors, and types. It isn't guaranteed to find everything, and will sometimes create false index entries, but it usually gets the job done fairly well. In particular, at present, functions are only indexed if a type signature is given for them.

Before hasktags, there used to be fptags and hstags, which did essentially the same job, however neither of these seem to be maintained any more.

10.1.1. Using tags with your editor

With NEdit, load the "tags" file using "File/Load Tags File". Use "Ctrl-D" to search for a tag.

With XEmacs, load the "TAGS" file using "visit-tags-table". Use "M-." to search for a tag.