137 lines
4.0 KiB
Hy
137 lines
4.0 KiB
Hy
;;; Hy anaphoric macros
|
|
;; Copyright 2017 the authors.
|
|
;; This file is part of Hy, which is free software licensed under the Expat
|
|
;; license. See the LICENSE.
|
|
|
|
;;; These macros make writing functional programs more concise
|
|
|
|
|
|
(defmacro ap-if [test-form then-form &optional else-form]
|
|
`(do
|
|
(setv it ~test-form)
|
|
(if it ~then-form ~else-form)))
|
|
|
|
|
|
(defmacro ap-each [lst &rest body]
|
|
"Evaluate the body form for each element in the list."
|
|
`(for [it ~lst] ~@body))
|
|
|
|
|
|
(defmacro ap-each-while [lst form &rest body]
|
|
"Evaluate the body form for each element in the list while the
|
|
predicate form evaluates to True."
|
|
(setv p (gensym))
|
|
`(do
|
|
(defn ~p [it] ~form)
|
|
(for [it ~lst]
|
|
(if (~p it)
|
|
~@body
|
|
(break)))))
|
|
|
|
|
|
(defmacro ap-map [form lst]
|
|
"Yield elements evaluated in the form for each element in the list."
|
|
(setv v (gensym 'v) f (gensym 'f))
|
|
`((fn []
|
|
(defn ~f [it] ~form)
|
|
(for [~v ~lst]
|
|
(yield (~f ~v))))))
|
|
|
|
|
|
(defmacro ap-map-when [predfn rep lst]
|
|
"Yield elements evaluated for each element in the list when the
|
|
predicate function returns True."
|
|
(setv f (gensym))
|
|
`((fn []
|
|
(defn ~f [it] ~rep)
|
|
(for [it ~lst]
|
|
(if (~predfn it)
|
|
(yield (~f it))
|
|
(yield it))))))
|
|
|
|
|
|
(defmacro ap-filter [form lst]
|
|
"Yield elements returned when the predicate form evaluates to True."
|
|
(setv pred (gensym))
|
|
`((fn []
|
|
(defn ~pred [it] ~form)
|
|
(for [val ~lst]
|
|
(if (~pred val)
|
|
(yield val))))))
|
|
|
|
|
|
(defmacro ap-reject [form lst]
|
|
"Yield elements returned when the predicate form evaluates to False"
|
|
`(ap-filter (not ~form) ~lst))
|
|
|
|
|
|
(defmacro ap-dotimes [n &rest body]
|
|
"Execute body for side effects `n' times, with it bound from 0 to n-1"
|
|
(unless (numeric? n)
|
|
(raise (TypeError (.format "{!r} is not a number" n))))
|
|
`(ap-each (range ~n) ~@body))
|
|
|
|
|
|
(defmacro ap-first [predfn lst]
|
|
"Yield the first element that passes `predfn`"
|
|
(with-gensyms [n]
|
|
`(do
|
|
(setv ~n None)
|
|
(ap-each ~lst (when ~predfn (setv ~n it) (break)))
|
|
~n)))
|
|
|
|
|
|
(defmacro ap-last [predfn lst]
|
|
"Yield the last element that passes `predfn`"
|
|
(with-gensyms [n]
|
|
`(do
|
|
(setv ~n None)
|
|
(ap-each ~lst (none? ~n)
|
|
(when ~predfn
|
|
(setv ~n it)))
|
|
~n)))
|
|
|
|
|
|
(defmacro ap-reduce [form lst &optional [initial-value None]]
|
|
"Anaphoric form of reduce, `acc' and `it' can be used for a form"
|
|
`(do
|
|
(setv acc ~(if (none? initial-value) `(get ~lst 0) initial-value))
|
|
(ap-each ~(if (none? initial-value) `(cut ~lst 1) lst)
|
|
(setv acc ~form))
|
|
acc))
|
|
|
|
|
|
(defmacro ap-pipe [var &rest forms]
|
|
"Pushes a value through several forms.
|
|
(Anaphoric version of -> and ->>)"
|
|
(if (empty? forms) var
|
|
`(ap-pipe (do (setv it ~var) ~(first forms)) ~@(rest forms))))
|
|
|
|
|
|
(defmacro ap-compose [&rest forms]
|
|
"Returns a function which is the composition of several forms."
|
|
`(fn [var] (ap-pipe var ~@forms)))
|
|
|
|
(deftag % [body]
|
|
"Returns a function with parameters implicitly determined by the presence in
|
|
the body of %i parameters. A %i symbol designates the ith parameter
|
|
(1-based, e.g. %1, %2, %3, etc.), or all remaining parameters for %&.
|
|
Nesting of #%() forms is not recommended."
|
|
(setv flatbody (flatten body))
|
|
`(fn [;; generate all %i symbols up to the maximum found in body
|
|
~@(genexpr (HySymbol (+ "%"
|
|
(str i)))
|
|
[i (range 1
|
|
;; find the maximum %i
|
|
(inc (max (+ (list-comp (int (cut a 1))
|
|
[a flatbody]
|
|
(and (symbol? a)
|
|
(.startswith a '%)
|
|
(.isdigit (cut a 1))))
|
|
[0]))))])
|
|
;; generate the &rest parameter only if '%& is present in body
|
|
~@(if (in '%& flatbody)
|
|
'(&rest %&)
|
|
'())]
|
|
(~@body)))
|