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Add protect macro.

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A more functional version of try catch.
This commit is contained in:
Calvin Rose 2019-12-09 17:32:02 -06:00
parent 4c5734c2ee
commit 1a6eb52f11
1 changed files with 11 additions and 1 deletions
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12
src/boot/boot.janet
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@ -218,11 +218,21 @@
f (gensym) f (gensym)
r (gensym)] r (gensym)]
~(let [,f (,fiber/new (fn [] ,body) :ie) ~(let [,f (,fiber/new (fn [] ,body) :ie)
,r (resume ,f)] ,r (,resume ,f)]
(if (= (,fiber/status ,f) :error) (if (= (,fiber/status ,f) :error)
(do (def ,err ,r) ,(if fib ~(def ,fib ,f)) ,;(tuple/slice catch 1)) (do (def ,err ,r) ,(if fib ~(def ,fib ,f)) ,;(tuple/slice catch 1))
,r)))) ,r))))
(defmacro protect
"Evaluate expressions, while capturing any errors. Evaluates to a tuple
of two elements. The first element is true if successful, false if an
error, and the second is the return value or error."
[& body]
(let [f (gensym) r (gensym)]
~(let [,f (,fiber/new (fn [] ,;body) :ie)
,r (,resume ,f)]
[(,not= :error (,fiber/status ,f)) ,r])))
(defmacro and (defmacro and
"Evaluates to the last argument if all preceding elements are true, otherwise "Evaluates to the last argument if all preceding elements are true, otherwise
evaluates to false." evaluates to false."