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Programs Accompanying the Thesis

The programs correspond to chapters 6, 7, 8 of part II. They are directly extracted from the thesis source file and listed in the same order as they are in the thesis. They were compiled with GHC version 7.8.3.

Page numbers in comments refer to the location of the code in a previous version of the thesis, so they might not correspond exactly to the last version.

Section headings are given in comments, in the format of the outshine minor mode of Emacs, which allows to navigate the structure of file easily and fold/unfold sections of the program, very useful given when the files are big. I give some instructions at the end of this file to configure Emacs properly.

  • Circular_6_1and2 contains the programs of chapter 6 section 1 and 2;
  • Circular_6_3 contains the programs of chapter 6 section 3;
  • Circular_7_1 contains the programs of chapter 7 section 1;
  • Circular_7_2to5 contains the programs of chapter 7 section 2 to 5.

The git repository ag-a-la-carte contains the implementation of the attribute grammar library discussed in section 8.4.

  • Desk is the example discussed in 8.4.1;
  • Repmin is another example not discussed in the thesis but related to chapter 6 and 7.

Note on the use of arrow operators

In the thesis we used a type variable ~> to stand for some Arrow so that a ~> b stands for an arrow from a to b. Such operator variables used to be allowed in GHC but they no longer are. Instead, we can define types as operators. Thus we can devise the following trick (borrowed from E. Kmett), using two type operators: - and ~> defined such that a -h~> b == h a b, for an arrow h. Those operators are defined in Circular_6_1and2.

Outshine minor mode

To use the outshine minor mode insert the following in your .emacs file. First install the package outshine, for instance using the following:

(require 'package)
(add-to-list 'package-archives
             '("melpa" . "http://melpa.milkbox.net/packages/"))
(package-initialize)
(unless (package-installed-p 'outshine)
   (package-install 'outshine))

Then activate it and use the correct regexp for recognising section headings, and load outline minor mode when entering Haskell mode.

(require 'outshine)
; recognise section headings in comments
(add-hook 'haskell-mode-hook  (lambda ()
    (setq outline-regexp "-- [*]\\{1,8\\} ")
    (outshine-fontify-headlines "-- [*]\\{1,8\\} ")))
(add-hook 'haskell-mode-hook 'outline-minor-mode)

Then the following keystrokes are active when the cursor is on a heading comment:

Keystroke Action
<TAB> folds/unfolds a section
<M-TAB> cycle through the following states:

  • SHOW ALL where the file is displayed as normal
  • OVERVIEW where only the main headings are shown
  • CONTENTS where all the headings are shown
<M-right> unfolds a section
<M-left> folds a section
<M-up> previous heading
<M-down> next heading

Additionally, you may want to rebind outline minor mode commands to navigate more easily. Those commands are valid anywhere in the file, not just on heading lines.

(defun outshine-extra-bindings ()
  (local-set-key (kbd "C-M-h") 'hide-body)
  (local-set-key (kbd "C-M-S-h") 'hide-sublevels)
  (local-set-key (kbd "C-M-a") 'show-all)
  (local-set-key (kbd "C-M-<left>") 'outline-up-heading)
  (local-set-key (kbd "C-M-<right>") 
                 (lambda () (interactive)
                   (outline-up-heading 1)
                   (outline-forward-same-level 1)))
  (local-set-key (kbd "C-M-<up>") 'outline-backward-same-level)
  (local-set-key (kbd "C-M-<down>") 'outline-forward-same-level))
(add-hook 'outline-minor-mode-hook 'outshine-extra-bindings)