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authorWilliam Carroll <wpcarro@gmail.com>2019-10-09T11·13+0100
committerWilliam Carroll <wpcarro@gmail.com>2019-12-24T15·21+0000
commit6b456c1b7a4f6899f063a6e65355af51901d9c7a (patch)
treecfc70d74818ae9fabdbbfb0cf16cce092e4c1a09 /configs/shared/.emacs.d/wpc/stack.el
parenta7c72adb2ebec1e497fc040eaf3551d564d61a5b (diff)
Massive configuration overhaul
Currently paying the price of months of non-diligent git usage.

Here's what has changed.

- Theming support in Gvcci and wpgtk
- Dropping support for i3
- Supporting EXWM
- Many Elisp modules
- Collapsed redundant directories in ./configs
Diffstat (limited to 'configs/shared/.emacs.d/wpc/stack.el')
-rw-r--r--configs/shared/.emacs.d/wpc/stack.el93
1 files changed, 93 insertions, 0 deletions
diff --git a/configs/shared/.emacs.d/wpc/stack.el b/configs/shared/.emacs.d/wpc/stack.el
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+++ b/configs/shared/.emacs.d/wpc/stack.el
@@ -0,0 +1,93 @@
+;;; stack.el --- Working with stacks in Elisp -*- lexical-binding: t -*-
+;; Author: William Carroll <wpcarro@gmail.com>
+
+;;; Commentary:
+;; A stack is a LIFO queue.
+;; The design goal here is to expose an intuitive API for working with stacks in
+;; non-mutative way.
+;;
+;; TODO: Consider naming a Functor instance "Mappable."
+;; TODO: Consider naming a Foldable instance "Reduceable."
+;;
+;; TODO: Consider implementing an instance for Mappable.
+;; TODO: Consider implementing an instance for Reduceable.
+
+;;; Code:
+
+(require 'list)
+
+(cl-defstruct stack xs)
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Create
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defun stack/new ()
+  "Create an empty stack."
+  (make-stack :xs '()))
+
+(defun stack/from-list (xs)
+  "Create a new stack from the list, `XS'."
+  (list/reduce (stack/new) #'stack/push xs))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Read
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defun stack/peek (xs)
+  "Look at the top element of `XS' without popping it off."
+  (->> xs
+       stack-xs
+       list/head))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Update
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defun stack/push (x xs)
+  "Push `X' on `XS'."
+  (struct/update stack
+                 xs
+                 (>> (list/cons x))
+                 xs))
+
+;; TODO: How to return something like {(list/head xs), (list/tail xs)} in Elixir
+;; TODO: How to handle popping from empty stacks?
+(defun stack/pop (xs)
+  "Return the stack, `XS', without the top element.
+Since I cannot figure out a nice way of return tuples in Elisp, if you want to
+look at the first element, use `stack/peek' before running `stack/pop'."
+  (struct/update stack
+                 xs
+                 (>> list/tail)
+                 xs))
+
+(defun stack/map-top (f xs)
+  "Apply F to the top element of XS."
+  (->> xs
+       stack/pop
+       (stack/push (funcall f (stack/peek xs)))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Miscellaneous
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defun stack/to-list (xs)
+  "Return XS as a list.
+The round-trip property of `stack/from-list' and `stack/to-list' should hold."
+  (->> xs
+       stack-xs
+       list/reverse))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Predicates
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; TODO: Create a macro that wraps `cl-defstruct' that automatically creates
+;; things like `new', `instance?'.
+(defun stack/instance? (xs)
+  "Return t if XS is a stack."
+  (stack-p xs))
+
+(provide 'stack)
+;;; stack.el ends here