2013-11-29 05:53:02 +01:00
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;;; Hy anaphoric macros
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2017-04-27 23:16:57 +02:00
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;; Copyright 2017 the authors.
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;; This file is part of Hy, which is free software licensed under the Expat
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;; license. See the LICENSE.
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2013-11-29 05:53:02 +01:00
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;;; These macros make writing functional programs more concise
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2015-06-17 00:11:55 +02:00
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(defmacro ap-if [test-form then-form &optional else-form]
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2017-02-04 02:03:06 +01:00
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`(do
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2017-10-26 20:53:08 +02:00
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(setv it ~test-form)
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(if it ~then-form ~else-form)))
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2013-12-25 18:11:25 +01:00
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2013-11-29 05:53:02 +01:00
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(defmacro ap-each [lst &rest body]
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2013-11-30 01:59:20 +01:00
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"Evaluate the body form for each element in the list."
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2013-12-31 19:35:31 +01:00
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`(for [it ~lst] ~@body))
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2013-11-29 05:53:02 +01:00
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2013-11-30 01:59:20 +01:00
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(defmacro ap-each-while [lst form &rest body]
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2015-12-08 14:43:47 +01:00
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"Evaluate the body form for each element in the list while the
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2013-11-30 01:59:20 +01:00
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predicate form evaluates to True."
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2017-02-04 02:03:06 +01:00
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(setv p (gensym))
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`(do
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(defn ~p [it] ~form)
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2013-12-31 19:35:31 +01:00
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(for [it ~lst]
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2017-02-04 02:03:06 +01:00
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(if (~p it)
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2017-10-26 20:53:08 +02:00
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~@body
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(break)))))
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2013-11-29 05:53:02 +01:00
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(defmacro ap-map [form lst]
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2013-11-30 01:59:20 +01:00
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"Yield elements evaluated in the form for each element in the list."
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2017-02-04 02:03:06 +01:00
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(setv v (gensym 'v) f (gensym 'f))
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`((fn []
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2017-10-26 20:53:08 +02:00
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(defn ~f [it] ~form)
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(for [~v ~lst]
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(yield (~f ~v))))))
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2013-11-29 05:53:02 +01:00
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(defmacro ap-map-when [predfn rep lst]
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"Yield elements evaluated for each element in the list when the
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predicate function returns True."
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2017-02-04 02:03:06 +01:00
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(setv f (gensym))
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`((fn []
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2017-10-26 20:53:08 +02:00
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(defn ~f [it] ~rep)
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(for [it ~lst]
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(if (~predfn it)
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(yield (~f it))
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(yield it))))))
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2013-11-29 05:53:02 +01:00
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(defmacro ap-filter [form lst]
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"Yield elements returned when the predicate form evaluates to True."
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(setv pred (gensym))
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`((fn []
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(defn ~pred [it] ~form)
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(for [val ~lst]
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(if (~pred val)
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(yield val))))))
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2013-12-25 20:18:09 +01:00
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(defmacro ap-reject [form lst]
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"Yield elements returned when the predicate form evaluates to False"
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`(ap-filter (not ~form) ~lst))
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(defmacro ap-dotimes [n &rest body]
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"Execute body for side effects `n' times, with it bound from 0 to n-1"
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(unless (numeric? n)
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(raise (TypeError (.format "{!r} is not a number" n))))
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2013-12-25 20:18:09 +01:00
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`(ap-each (range ~n) ~@body))
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(defmacro ap-first [predfn lst]
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"Yield the first element that passes `predfn`"
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2014-05-15 20:11:24 +02:00
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(with-gensyms [n]
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`(do
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(setv ~n None)
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2014-05-15 20:11:24 +02:00
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(ap-each ~lst (when ~predfn (setv ~n it) (break)))
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~n)))
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2013-12-25 20:18:09 +01:00
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(defmacro ap-last [predfn lst]
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"Yield the last element that passes `predfn`"
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2014-05-15 20:11:24 +02:00
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(with-gensyms [n]
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`(do
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(setv ~n None)
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2014-05-15 20:11:24 +02:00
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(ap-each ~lst (none? ~n)
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(when ~predfn
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(setv ~n it)))
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~n)))
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2013-12-25 20:18:09 +01:00
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(defmacro ap-reduce [form lst &optional [initial-value None]]
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"Anaphoric form of reduce, `acc' and `it' can be used for a form"
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`(do
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2017-10-26 20:53:08 +02:00
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(setv acc ~(if (none? initial-value) `(get ~lst 0) initial-value))
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(ap-each ~(if (none? initial-value) `(cut ~lst 1) lst)
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(setv acc ~form))
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acc))
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2015-04-03 23:02:39 +02:00
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(defmacro ap-pipe [var &rest forms]
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"Pushes a value through several forms.
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(Anaphoric version of -> and ->>)"
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(if (empty? forms) var
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2017-02-04 02:03:06 +01:00
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`(ap-pipe (do (setv it ~var) ~(first forms)) ~@(rest forms))))
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2015-04-03 23:02:39 +02:00
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(defmacro ap-compose [&rest forms]
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"Returns a function which is the composition of several forms."
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`(fn [var] (ap-pipe var ~@forms)))
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2015-08-12 02:11:33 +02:00
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2015-08-12 16:45:43 +02:00
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(defmacro xi [&rest body]
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2015-08-12 02:11:33 +02:00
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"Returns a function with parameters implicitly determined by the presence in
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the body of xi parameters. An xi symbol designates the ith parameter
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(1-based, e.g. x1, x2, x3, etc.), or all remaining parameters for xi itself.
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2017-02-23 00:36:52 +01:00
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This is not a replacement for fn. The xi forms cannot be nested. "
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2015-08-12 02:11:33 +02:00
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(setv flatbody (flatten body))
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2017-02-23 00:36:52 +01:00
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`(fn [;; generate all xi symbols up to the maximum found in body
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2017-10-26 20:53:08 +02:00
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~@(genexpr (HySymbol (+ "x"
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(str i)))
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[i (range 1
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;; find the maximum xi
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(inc (max (+ (list-comp (int (cut a 1))
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[a flatbody]
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(and (symbol? a)
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(.startswith a 'x)
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(.isdigit (cut a 1))))
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[0]))))])
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;; generate the &rest parameter only if 'xi is present in body
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~@(if (in 'xi flatbody)
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'(&rest xi)
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'())]
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2015-08-12 16:45:43 +02:00
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(~@body)))
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