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Add generator expressions for easier iteration.

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Similar to python generator, but with the same
syntax as the loop macro.
This commit is contained in:
Calvin Rose
2018-11-20 21:48:06 -05:00
parent 1e87b01e02
commit 184fe31e0c
4 changed files with 62 additions and 23 deletions
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41
src/core/core.janet
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@@ -271,7 +271,9 @@
\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
\t:keys - Iterate over the keys in a data structure.\n
\t:in - Iterate over the values in an indexed data structure or byte sequence.\n\n
\t:in - Iterate over the values in an indexed data structure or byte sequence.\n
\t:generate - Iterate over values yielded from a fiber. Can be paired with the generator
function for the producer/consumer pattern.\n\n
loop also accepts conditionals to refine the looping further. Conditionals are of
the form:\n\n
\t:modifier argument\n\n
@@ -294,11 +296,9 @@
(if (>= i len)
(tuple.prepend body 'do)
(do
(def {
i bindings
(def {i bindings
(+ i 1) verb
(+ i 2) object
} head)
(+ i 2) object} head)
(if (keyword? bindings)
(case bindings
:while (do
@@ -371,8 +371,25 @@
(tuple 'def bindings (tuple get $indexed $i))
subloop
(tuple ':= $i (tuple + 1 $i)))))
:generate (do
(def $fiber (gensym))
(def $yieldval (gensym))
(def preds @['and
(do
(def s (gensym))
(tuple 'do
(tuple 'def s (tuple fiber.status $fiber))
(tuple 'or (tuple = s :pending) (tuple = s :new))))])
(def subloop (doone (+ i 3) preds))
(tuple 'do
(tuple 'def $fiber object)
(tuple 'var $yieldval (tuple resume $fiber))
(tuple 'while (tuple.slice preds 0)
(tuple 'def bindings $yieldval)
subloop
(tuple := $yieldval (tuple resume $fiber)))))
(error (string "unexpected loop verb: " verb)))))))
(doone 0 nil))
(tuple 'do (doone 0 nil) nil))
(defmacro fora
"Similar to loop, but accumulates the loop body into an array and returns that.
@@ -398,6 +415,13 @@
(tuple.prepend body 'do)))
(tuple tuple.slice $accum 0)))
(defmacro generate
"Create a generator expression using the loop syntax. Returns a fiber
that yields all values inside the loop in order. See loop for details."
[head & body]
(tuple fiber.new
(tuple 'fn @[] (tuple 'loop head (tuple yield (tuple.prepend body 'do))))))
(defn sum [xs]
(var accum 0)
(loop [x :in xs] (+= accum x))
@@ -1146,7 +1170,6 @@ value, one key will be ignored."
(if (bytes? x) x (string.pretty x))
"\n")
(when f
(def st (fiber.stack f))
(loop
[{:function func
:tail tail
@@ -1155,7 +1178,7 @@ value, one key will be ignored."
:name name
:source source
:line source-line
:column source-col} :in st]
:column source-col} :in (fiber.stack f)]
(file.write stderr " in")
(when c (file.write stderr " cfunction"))
(if name
@@ -1329,7 +1352,7 @@ value, one key will be ignored."
(def buf @"")
(default onvalue (fn [x]
(put newenv '_ @{:value x})
(print (string.pretty x 8 buf))
(print (string.pretty x 20 buf))
(buffer.clear buf)))
(default onerr default-error-handler)
(run-context newenv getchunk onvalue onerr "repl"))