14fddbe6c3
Give `require` the same features as `import` You can now do (require foo), (require [foo [a b c]]), (require [foo [*]]), and (require [foo :as bar]). The first and last forms get you macros named foo.a, foo.b, etc. or bar.a, bar.b, etc., respectively. The second form only gets the macros in the list. Implements #1118 and perhaps partly addresses #277. N.B. The new meaning of (require foo) will cause all existing code that uses macros to break. Simply replace these forms with (require [foo [*]]) to get your code working again. There's a bit of a hack involved in the forms (require foo) or (require [foo :as bar]). When you call (foo.a ...) or (bar.a ...), Hy doesn't actually look inside modules. Instead, these (require ...) forms give the macros names that have periods in them, which happens to work fine with the way Hy finds and interprets macro calls. * Make `require` syntax stricter and add tests * Update documentation for `require` * Documentation wording improvements * Allow :as in `require` name lists
94 lines
3.6 KiB
Hy
94 lines
3.6 KiB
Hy
;;; Hy tail-call optimization
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;;
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;; Copyright (c) 2014 Clinton Dreisbach <clinton@dreisbach.us>
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;; Copyright (c) 2014 Paul R. Tagliamonte <tag@pault.ag>
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;;
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;; Permission is hereby granted, free of charge, to any person obtaining a
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;; copy of this software and associated documentation files (the "Software"),
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;; to deal in the Software without restriction, including without limitation
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;; the rights to use, copy, modify, merge, publish, distribute, sublicense,
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;; and/or sell copies of the Software, and to permit persons to whom the
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;; Software is furnished to do so, subject to the following conditions:
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;;
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;; The above copyright notice and this permission notice shall be included in
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;; all copies or substantial portions of the Software.
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;;
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;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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;; THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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;; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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;; DEALINGS IN THE SOFTWARE.
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;;
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;;; The loop/recur macro allows you to construct functions that use tail-call
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;;; optimization to allow arbitrary levels of recursion.
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(defn --trampoline-- [f]
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"Wrap f function and make it tail-call optimized."
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;; Takes the function "f" and returns a wrapper that may be used for tail-
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;; recursive algorithms. Note that the returned function is not side-effect
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;; free and should not be called from anywhere else during tail recursion.
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(setv result None)
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;; We have to put this in a list because of Python's
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;; weirdness around local variables.
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;; Assigning directly to it later would cause it to
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;; shadow in a new scope.
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(setv active [False])
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(setv accumulated [])
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(fn [&rest args]
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(.append accumulated args)
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(when (not (first active))
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(assoc active 0 True)
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(while (> (len accumulated) 0)
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(setv result (apply f (.pop accumulated))))
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(assoc active 0 False)
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result)))
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(defn recursive-replace [old-term new-term body]
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"Recurses through lists of lists looking for old-term and replacing it with new-term."
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((type body)
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(list-comp (cond
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[(= term old-term) new-term]
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[(instance? hy.HyList term)
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(recursive-replace old-term new-term term)]
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[True term]) [term body])))
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(defmacro/g! fnr [signature &rest body]
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(let [new-body (recursive-replace 'recur g!recur-fn body)]
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`(do
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(import [hy.contrib.loop [--trampoline--]])
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(with-decorator
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--trampoline--
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(def ~g!recur-fn (fn [~@signature] ~@new-body)))
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~g!recur-fn)))
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(defmacro defnr [name lambda-list &rest body]
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(if (not (= (type name) HySymbol))
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(macro-error name "defnr takes a name as first argument"))
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`(do (require hy.contrib.loop)
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(setv ~name (hy.contrib.loop.fnr ~lambda-list ~@body))))
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(defmacro/g! loop [bindings &rest body]
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;; Use inside functions like so:
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;; (defn factorial [n]
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;; (loop [[i n]
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;; [acc 1]]
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;; (if (= i 0)
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;; acc
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;; (recur (dec i) (* acc i)))))
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;;
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;; If recur is used in a non-tail-call position, None is returned, which
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;; causes chaos. Fixing this to detect if recur is in a tail-call position
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;; and erroring if not is a giant TODO.
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(let [fnargs (map (fn [x] (first x)) bindings)
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initargs (map second bindings)]
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`(do (require hy.contrib.loop)
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(hy.contrib.loop.defnr ~g!recur-fn [~@fnargs] ~@body)
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(~g!recur-fn ~@initargs))))
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