refactor let symbol expansion to a class
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gilch
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20b4342d40
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bcc93fb1fe
@ -93,6 +93,169 @@ Arguments without a header are under None.
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(.append (get sections header) arg)))
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sections)
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(defclass SymbolExpander[]
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(defn expand-symbols [self form &optional protected quote-level]
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(if (none? protected)
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(setv protected self.protected))
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(if (none? quote-level)
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(setv quote-level self.quote-level))
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(.expand (SymbolExpander form self.expander protected quote-level)))
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(defn __init__ [self form expander
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&optional
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[protected (frozenset)]
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[quote-level 0]]
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(setv self.form form
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self.expander expander
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self.protected protected
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self.quote-level quote-level))
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(defn traverse [self form &optional protected quote-level]
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(if (none? protected)
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(setv protected self.protected))
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(if (none? quote-level)
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(setv quote-level self.quote-level))
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(walk (partial self.expand-symbols
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:protected protected
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:quote-level quote-level)
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identity
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form))
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;; manages quote levels
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(defn +quote [self &optional [x 1]]
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`(~(self.head) ~@(self.traverse (self.tail)
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:quote-level (+ self.quote-level x))))
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(defn handle-dot [self]
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`(. ~@(walk (fn [form]
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(if (symbol? form)
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form ; don't expand attrs
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(self.expand-symbols form)))
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identity
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(self.tail))))
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(defn head [self]
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(first self.form))
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(defn tail [self]
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(cut self.form 1))
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(defn handle-except [self]
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(setv tail (self.tail))
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;; protect the "as" name binding the exception
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`(~(self.head) ~@(self.traverse tail (| self.protected
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(if (and tail
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(-> tail
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first
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len
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(= 2)))
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#{(first (first tail))}
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#{})))))
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(defn handle-args-list [self]
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(setv protected #{}
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argslist `[])
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(for [[header section] (-> self (.tail) first lambda-list .items)]
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(if header (.append argslist header))
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(cond [(in header [None '&rest '&kwargs])
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(.update protected (-> section flatten set))
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(.extend argslist section)]
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[(in header '[&optional &kwonly])
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(for [pair section]
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(cond [(coll? pair)
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(.add protected (first pair))
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(.append argslist
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`[~(first pair)
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~(self.expand-symbols (second pair))])]
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[True
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(.add protected pair)
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(.append argslist pair)]))]
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[(= header '&key)
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(setv &key-dict '{})
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(for [[k v] (-> section first partition)]
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(.add protected k)
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(.append &key-dict k)
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(.append &key-dict (self.expand-symbols v)))
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(.append argslist &key-dict)]))
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(, protected argslist))
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(defn handle-fn [self]
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(setv [protected argslist] (self.handle-args-list))
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`(~(self.head) ~argslist
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~@(self.traverse (cut (self.tail) 1)(| protected self.protected))))
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;; don't expand symbols in quotations
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(defn handle-quoted [self]
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(if (call? self.form)
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(if (in (self.head) '[unquote unquote-splice]) (self.+quote -1)
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(= (self.head) 'quasiquote) (self.+quote)
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(self.handle-coll))
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(if (coll? self.form)
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(self.handle-coll)
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(self.handle-base))))
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;; convert dotted names to the standard special form
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(defn convert-dotted-symbol [self]
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(self.expand-symbols `(. ~@(map HySymbol (.split self.form '.)))))
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(defn expand-symbol [self]
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(if (not-in self.form self.protected)
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(self.expander self.form)
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(self.handle-base)))
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(defn handle-symbol [self]
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(if (and self.form
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(not (.startswith self.form '.))
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(in '. self.form))
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(self.convert-dotted-symbol)
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(self.expand-symbol)))
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(defn handle-global [self]
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(.update self.protected (set (self.tail)))
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(self.handle-base))
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(defn handle-defclass [self]
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;; don't expand the name of the class
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`(~(self.head) ~(first (self.tail))
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~@(self.traverse (cut (self.tail) 1))))
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(defn handle-special-form [self]
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;; don't expand other special form symbols in head position
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`(~(self.head) ~@(self.traverse (self.tail))))
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(defn handle-base [self]
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self.form)
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(defn handle-coll [self]
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;; recursion
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(self.traverse self.form))
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;; We have to treat special forms differently.
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;; Quotation should suppress symbol expansion,
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;; and local bindings should shadow those made by let.
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(defn handle-call [self]
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(setv head (first self.form))
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(if (in head '[fn fn*]) (self.handle-fn)
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(in head '[import quote]) (self.handle-base)
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(= head 'except) (self.handle-except)
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(= head ".") (self.handle-dot)
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(= head 'global) (self.handle-global)
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(= head 'defclass) (self.handle-defclass)
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(= head 'quasiquote) (self.+quote)
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;; must be checked last!
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(in head special-forms) (self.handle-special-form)
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;; Not a special form. Traverse it like a coll
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(self.handle-coll)))
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(defn expand [self]
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"the main entry point. Call this to do the expansion"
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(setv form self.form)
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(if self.quote-level (self.handle-quoted)
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(symbol? form) (self.handle-symbol)
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(call? form) (self.handle-call)
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(coll? form) (self.handle-coll)
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;; recursive base case--it's an atom. Put it back.
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(self.handle-base))))
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(defmacro let [bindings &rest body]
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"
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sets up lexical bindings in its body
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@ -120,122 +283,19 @@ as can nested let forms.
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;; pre-expanding the body means we only have to worry about a small number
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;; of special forms
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(setv body (macroexpand-all body)
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bound-symbols (cut bindings None None 2)
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quote-level [0])
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bound-symbols (cut bindings None None 2))
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(for [k bound-symbols]
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(if-not (symbol? k)
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(macro-error k "let can only bind to symbols")
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(if (in '. k)
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(macro-error k "let binding symbols may not contain a dot"))))
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;; sets up the recursion call
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(defn expand-symbols [protected-symbols form]
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(defn traverse [form &optional [protected-symbols protected-symbols]]
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(walk (partial expand-symbols protected-symbols)
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identity
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form))
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;; manages quote levels
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(defn +quote [&optional [x 1]]
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(setv head (first form))
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(+= (get quote-level 0) x)
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(setv res (traverse (cut form 1)))
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(-= (get quote-level 0) x)
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`(~head ~@res))
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(cond [(get quote-level 0) ; don't expand symbols in quotations
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(if (call? form)
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(cond [(in (first form) '[unquote unquote-splice])
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(+quote -1)]
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[(= (first form) 'quasiquote)
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(+quote)]
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[True (traverse form)])
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(if (coll? form)
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(traverse form)
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form))]
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;; symbol expansions happen here.
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[(symbol? form)
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(if (and form
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(not (.startswith form '.))
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(in '. form))
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;; convert dotted names to the standard special form
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(expand-symbols protected-symbols
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`(. ~@(map HySymbol (.split form '.))))
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;; else expand if applicable
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(if (and (in form bound-symbols)
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(not-in form protected-symbols))
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(HySymbol (+ g!let "::" form))
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form))]
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;; We have to treat special forms differently.
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;; Quotation should suppress symbol expansion,
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;; and local bindings should shadow those made by let.
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[(call? form)
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(setv head (first form))
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(setv tail (cut form 1))
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(cond [(in head '[fn fn*])
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(setv body (cut tail 1)
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protected #{}
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fn-bindings `[])
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(for [[header section] (-> tail first lambda-list .items)]
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(if header (.append fn-bindings header))
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(cond [(in header [None '&rest '&kwargs])
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(.update protected (-> section flatten set))
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(.extend fn-bindings section)]
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[(in header '[&optional &kwonly])
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(for [pair section]
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(cond [(coll? pair)
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(.add protected (first pair))
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(.append fn-bindings
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`[~(first pair)
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~(expand-symbols protected-symbols
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(second pair))])]
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[True
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(.add protected pair)
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(.append fn-bindings pair)]))]
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[(= header '&key)
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(setv &key-dict '{})
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(for [[k v] (-> section first partition)]
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(.add protected k)
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(.append &key-dict k)
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(.append &key-dict (expand-symbols protected-symbols
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v)))
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(.append fn-bindings &key-dict)]))
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`(~head ~fn-bindings
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~@(traverse body (| protected protected-symbols)))]
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[(= head 'except)
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;; protect the "as" name binding the exception
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`(~head ~@(traverse tail (| protected-symbols
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(if (and tail
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(-> tail
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first
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len
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(= 2)))
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#{(first (first tail))}
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#{}))))]
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[(= head ".")
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`(. ~@(walk (fn [form]
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(if (symbol? form)
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form ; don't expand attrs
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(expand-symbols protected-symbols
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form)))
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identity
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tail))]
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[(= head 'global)
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(.update protected-symbols (set tail))
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form]
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[(in head '[import quote]) form]
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[(= head 'defclass)
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;; don't expand the name of the class
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`(~head ~(first tail) ~@(traverse (cut tail 1)))]
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[(= head 'quasiquote) (+quote)]
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;; don't expand other special form symbols in head position
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[(in head special-forms) `(~head ~@(traverse tail))]
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;; Not a special form. Traverse it like a coll
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[True (traverse form)])]
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[(coll? form) (traverse form)]
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;; recursive base case--it's an atom. Put it back.
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[True form]))
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(expand-symbols #{}
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`(do
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(setv ~@bindings)
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~@body)))
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(.expand (SymbolExpander `(do
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(setv ~@bindings)
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~@body)
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(fn [symbol]
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(if (in symbol bound-symbols)
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(HySymbol (+ g!let "::" symbol))
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symbol)))))
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#_[special cases for let
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;; Symbols containing a dot should be converted to this form.
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