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Add label macro.

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A lexically scoped version of prompt is often useful.
This commit is contained in:
Calvin Rose 2020-02-23 17:15:04 -06:00
parent 59d288c429
commit 05bd5767de
1 changed files with 10 additions and 2 deletions
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12
src/boot/boot.janet
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@ -300,7 +300,7 @@
(propagate ,r ,f)))))
(defmacro prompt
"Set up a prompt point that can be aborted to. Tag should be a value
"Set up a checkpoint that can be returned to. Tag should be a value
that is used in a return statement, like a keyword."
[tag & body]
(with-syms [res target payload fib]
@ -312,9 +312,17 @@
,payload
(propagate ,res ,fib)))))
(defmacro label
"Set a label point that is lexically scoped. Name should be a symbol
that will be bound to the label."
[name & body]
~(do
(def ,name ',(gensym))
,(apply prompt name body)))
(defn return
"Return to a prompt point."
[to value]
[to &opt value]
(signal 0 [to value]))
(defmacro with