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(ns lang.lexer
(:require [clojure.template :refer [do-template]]
[clojure.core.match :refer [match]]
[lang.util :as &util :refer [exec return* return fail fail*
repeat-m try-m try-all-m]]))
(declare lex-form)
;; [Utils]
(defn ^:private lex-regex [regex]
(fn [text]
(if-let [[match] (re-find regex text)]
(return* (.substring text (.length match)) match)
(fail* (str "Pattern failed: " regex " -- " text)))))
(defn ^:private lex-str [prefix]
(fn [text]
(if (.startsWith text prefix)
(return* (.substring text (.length prefix)) prefix)
(fail* (str "String failed: " prefix " -- " text)))))
;; [Lexers]
(def ^:private lex-white-space (lex-regex #"^(\s+)"))
(def ^:private lex-list
(exec [_ (lex-str "(")
members (repeat-m lex-form)
_ (lex-str ")")]
(return [::list members])))
(def ^:private lex-tuple
(exec [_ (lex-str "[")
members (repeat-m lex-form)
_ (lex-str "]")]
(return [::tuple members])))
(def +ident-re+ #"^([a-zA-Z\-\+\_\=!@$%^&*<>\.,/\\\|'][a-zA-Z0-9\-\+\_\=!@$%^&*<>\.,/\\\|']*)")
(do-template [<name> <tag> <regex>]
(def <name>
(exec [token (lex-regex <regex>)]
(return [<tag> token])))
^:private lex-int ::int #"^(0|[1-9][0-9]*)"
^:private lex-ident ::ident +ident-re+)
(def ^:private lex-tag
(exec [_ (lex-str "#")
token (lex-regex +ident-re+)]
(return [::tag token])))
(def ^:private lex-form
(exec [_ (try-m lex-white-space)
form (try-all-m [lex-int
lex-ident
lex-tag
lex-list
lex-tuple])
_ (try-m lex-white-space)]
(return form)))
;; [Interface]
(defn lex [text]
(match ((repeat-m lex-form) text)
[::&util/ok [?state ?forms]]
(if (empty? ?state)
?forms
(assert false (str "Unconsumed input: " ?state)))
[::&util/failure ?message]
(assert false ?message)))
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