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FIX don't eval either twice in bind

This commit is contained in:
Nathan Dwarshuis 2022-04-27 23:44:14 -04:00
parent 21449ad792
commit 19077c72c9
1 changed files with 6 additions and 4 deletions
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8
local/lib/either/either.el
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@ -39,10 +39,12 @@ left/right slot."
(defmacro either>>= (either form)
"Bind EITHER to FORM where the right slot is bound to 'it'."
(declare (indent 1))
`(pcase ,either
(`(:left ,_) ,either)
(let ((e (make-symbol "--either")))
`(let ((,e ,either))
(pcase ,e
(`(:left ,_) ,e)
(`(:right ,it) ,form)
(e (error "Learn to use monads, dummy; this isn't one: %s" e))))
(e (error "Learn to use monads, dummy; this isn't one: %s" e))))))
(defun either-foldM (fun init xs)
"Mondically apply FUN to XS (a list).