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Code Issues 1 Releases Wiki Activity

Add :down verb to loop macro.

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Also remove with-idemp from core, which was both confusing
(to the author) and not generally useful.
This commit is contained in:
Calvin Rose
2019-03-03 23:52:20 -05:00
parent a4cc23971f
commit 1b9591b5e3
1 changed files with 35 additions and 18 deletions
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53
src/core/core.janet
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@@ -119,23 +119,6 @@
:struct true})
(fn idempotent? [x] (not (get non-atomic-types (type x))))))
(defmacro with-idemp
"Return janet code body that has been prepended
with a binding of form to atom. If form is a non-idempotent
form (a function call, etc.), make sure the resulting
code will only evaluate once, even if body contains multiple
copies of binding. In body, use binding instead of form."
[binding form & body]
(def $result (gensym))
(def $form (gensym))
~(do
(def ,$form ,form)
(def ,binding (if (idempotent? ,$form) ,$form (gensym)))
(def ,$result (do ,;body))
(if (= ,$form ,binding)
,$result
(tuple 'do (tuple 'def ,binding ,$form) ,$result))))
# C style macros and functions for imperative sugar. No bitwise though.
(defn inc "Returns x + 1." [x] (+ x 1))
(defn dec "Returns x - 1." [x] (- x 1))
@@ -282,7 +265,8 @@
and object is any janet expression. The available verbs are:\n\n
\t:iterate - repeatedly evaluate and bind to the expression while it is truthy.\n
\t:range - loop over a range. The object should be two element tuple with a start
and end value. The range is half open, [start, end).\n
and end value, and an optional postive step. The range is half open, [start, end).\n
\t:down - Same as range, but loops in reverse.\n
\t:keys - Iterate over the keys in a data structure.\n
\t:pairs - Iterate over the keys value pairs in a data structure.\n
\t:in - Iterate over the values in an indexed data structure or byte sequence.\n
@@ -359,6 +343,20 @@
(tuple 'def bindings $iter)
subloop
(tuple 'set $iter (tuple + $iter inc)))))
:down (do
(def [start end _dec] object)
(def dec (if _dec _dec 1))
(def endsym (gensym))
(def $iter (gensym))
(def preds @['and (tuple > $iter endsym)])
(def subloop (doone (+ i 3) preds))
(tuple 'do
(tuple 'var $iter start)
(tuple 'def endsym end)
(tuple 'while (tuple/slice preds)
(tuple 'def bindings $iter)
subloop
(tuple 'set $iter (tuple - $iter dec)))))
:keys (do
(def $dict (gensym))
(def $iter (gensym))
@@ -1111,6 +1109,24 @@ value, one key will be ignored."
###
###
(defmacro- with-idemp
"Return janet code body that has been prepended
with a binding of form to atom. If form is a non-idempotent
form (a function call, etc.), make sure the resulting
code will only evaluate once, even if body contains multiple
copies of binding. In body, use binding instead of form."
[binding form & body]
(def $result (gensym))
(def $form (gensym))
~(do
(def ,$form ,form)
(def ,binding (if (idempotent? ,$form) ,$form (gensym)))
(def ,$result (do ,;body))
(if (= ,$form ,binding)
,$result
(tuple 'do (tuple 'def ,binding ,$form) ,$result))))
# Sentinel value for mismatches
(def- sentinel ~',(gensym))
@@ -1184,6 +1200,7 @@ value, one key will be ignored."
(put _env 'sentinel nil)
(put _env 'match-1 nil)
(put _env 'with-idemp nil)
###
###