85 lines
2.6 KiB
EmacsLisp
85 lines
2.6 KiB
EmacsLisp
;; State --- State library of FG42 -*- lexical-binding: t; -*-
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;;
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;; Copyright (c) 2010-2020 Sameer Rahmani & Contributors
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;;
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;; Author: Sameer Rahmani <lxsameer@gnu.org>
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;; URL: https://gitlab.com/FG42/FG42
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;; Version: 3.0.0
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;;
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;; This program is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;;
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;; This program is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;;
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;; You should have received a copy of the GNU General Public License
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;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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;;
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;;; Commentary:
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;; Cubes are the building blocks of any `FG42' editor. Each `cube' is a
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;; unit which defines different abilities in a deterministic and idempotent
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;; way. Cubes are composable and a composition of cubes creates an editor.
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;;
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;;; Code:
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(require 'fg42/utils)
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(defun fg42/state-return (x)
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"Return a state monad containing X."
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(lambda (state)
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(cons state x)))
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(defun fg42/state-bind-maker (binder-fn)
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"Return a bind function for state monad.
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It creates a bind function that binds monadic functions by applying BINDER-FN
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to the return state and the value inside the monad before binding them.
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The BINDER-FN has to return a cons in form of (state . prev-v)."
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(lambda (m f)
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"Applys F on the M monad."
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(lambda (state)
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(let* ((v (funcall m state))
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(new-v (funcall (f (cdr v)) (car v))))
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(funcall binder-fn
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;; State
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(car new-v)
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;; Value of in the monad from M
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(cdr new-v))))))
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(defun fg42/state-unit ()
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"Create a new state monad.
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This monad describes the entire editor configuration"
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;; Why not a cl-struct ?
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;; Because first, we want it to be human readable
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(lambda (state)
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(cons
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(list '(:mode->keybindings . ())
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'(:mode->prefix . ())
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'(:mode->fn . ())
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'(:cubes . ()))
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())))
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(defun fg42/state-get (k &optional default)
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"Return the value of the given K from the STATE.
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It will return DEFAULT in case of a missing key."
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(lambda (state)
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(or (cdr (assoc k state)) default)))
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(defun fg42/state-cons (k v)
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"Add the given value V to the list addressed by key K on STATE."
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(lambda (state)
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(cons (cons k (cons v (or (fg42/state-get state k) '()))) state)))
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(provide 'fg42/state)
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;;; state.el ends here
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