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jupyter-do

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Nathaniel Nicandro 2020-05-14 21:19:43 -05:00
parent b32d99db68
commit d364bbfcb1
1 changed files with 14 additions and 8 deletions
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22
jupyter-monads.el
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@ -101,13 +101,20 @@ IO-VALUE and IO-FN, the I/O context is maintained."
`(let ((jupyter-current-io ,io))
,@body))
;; do takes IO-actions and sequences them.
;; do (for the IO monad) takes IO actions, functions of one argument
;; that return IO values (values with type `jupyter-delayed'), and
;; returns the actions composed. In the IO monad, composition is
;; equivalent to performing one IO action after the other. The result
;; of one action being bound to the next. The initial action is bound
;; to nil.
;;
;; Based on explanations at
;; https://wiki.haskell.org/Introduction_to_Haskell_IO/Actions
(defmacro jupyter-do (&rest io-fns)
"Bind IO-FNS in the current I/O context.
Bind nil to the first function in IO-FNS, then bind the result to
the second function, and so on. Return the result of evaluating
the last element. Each element of IO-FNS must return a delayed
value."
"Return an I/O action composing all IO-FNS.
The action evaluates each of IO-FNS in sequence, binding the
result of one action to the next. The initial action is bound to
nil."
(declare (indent 0))
(if (zerop (length io-fns)) 'nil
(letrec ((after-chain
@ -116,8 +123,7 @@ value."
'jupyter-io-nil
`(jupyter-after ,(funcall after-chain (cdr io-fns))
,(car io-fns))))))
`(jupyter-bind-delayed ,(funcall after-chain (reverse io-fns))
(lambda (value) (jupyter-return-delayed value))))))
,(funcall after-chain (reverse io-fns)))))
(defun jupyter-after (io-value io-fn)
"Return an I/O action that binds IO-VALUE to IO-FN.