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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-forms lex-list lex-tuple lex-record lex-tag)
;; [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-regex2 [regex]
(fn [text]
(if-let [[match tok1 tok2] (re-find regex text)]
(return* (.substring text (.length match)) [tok1 tok2])
(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)))))
(defn ^:private escape-char [escaped]
(condp = escaped
"\\t" (return "\t")
"\\b" (return "\b")
"\\n" (return "\n")
"\\r" (return "\r")
"\\f" (return "\f")
"\\\"" (return "\"")
"\\\\" (return "\\")
;; else
(fail (str "Unknown escape character: " escaped))))
(def ^:private lex-string-body
(try-all-m [(exec [[prefix escaped] (lex-regex2 #"(?s)^([^\"\\]*)(\\.)")
;; :let [_ (prn '[prefix escaped] [prefix escaped])]
unescaped (escape-char escaped)
;; :let [_ (prn 'unescaped unescaped)]
postfix lex-string-body
;; :let [_ (prn 'postfix postfix)]
;; :let [_ (prn 'FULL (str prefix unescaped postfix))]
]
(return (str prefix unescaped postfix)))
(lex-regex #"(?s)^([^\"\\]*)")]))
;; [Lexers]
(def ^:private lex-white-space (lex-regex #"^(\s+)"))
(def +ident-re+ #"^([a-zA-Z\-\+\_\=!@$%^&*<>\.,/\\\|':\~][0-9a-zA-Z\-\+\_\=!@$%^&*<>\.,/\\\|':\~]*)")
(do-template [<name> <tag> <regex>]
(def <name>
(exec [token (lex-regex <regex>)]
(return [<tag> token])))
^:private lex-boolean ::boolean #"^(true|false)"
^:private lex-float ::float #"^(0|[1-9][0-9]*)\.[0-9]+"
^:private lex-int ::int #"^(0|[1-9][0-9]*)"
^:private lex-ident ::ident +ident-re+)
(def ^:private lex-char
(exec [_ (lex-str "#\"")
token (try-all-m [(exec [escaped (lex-regex #"^(\\.)")]
(escape-char escaped))
(lex-regex #"^(.)")])
_ (lex-str "\"")]
(return [::char token])))
(def ^:private lex-string
(exec [_ (lex-str "\"")
;; state &util/get-state
;; :let [_ (prn 'PRE state)]
token lex-string-body
_ (lex-str "\"")
;; state &util/get-state
;; :let [_ (prn 'POST state)]
]
(return [::string token])))
(def ^:private lex-single-line-comment
(exec [_ (lex-str "##")
comment (lex-regex #"^([^\n]*)")
_ (lex-regex #"^(\n?)")
;; :let [_ (prn 'comment comment)]
]
(return [::comment comment])))
(def ^:private lex-multi-line-comment
(exec [_ (lex-str "#(")
;; :let [_ (prn 'OPEN)]
;; comment (lex-regex #"^(#\(.*\)#)")
comment (try-all-m [(lex-regex #"(?is)^((?!#\().)*?(?=\)#)")
(exec [pre (lex-regex #"(?is)^(.+?(?=#\())")
;; :let [_ (prn 'PRE pre)]
[_ inner] lex-multi-line-comment
;; :let [_ (prn 'INNER inner)]
post (lex-regex #"(?is)^(.+?(?=\)#))")
;:let [_ (prn 'POST post)]
]
(return (str pre "#(" inner ")#" post)))])
;; :let [_ (prn 'COMMENT comment)]
_ (lex-str ")#")
;; :let [_ (prn 'CLOSE)]
;; :let [_ (prn 'multi-comment comment)]
]
(return [::comment comment])))
(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-boolean
lex-float
lex-int
lex-char
lex-string
lex-ident
lex-tag
lex-list
lex-tuple
lex-record
lex-single-line-comment
lex-multi-line-comment])
_ (try-m lex-white-space)]
(return form)))
(def lex-forms
(exec [forms (repeat-m lex-form)]
(return (filter #(match %
[::comment _]
false
_
true)
forms))))
(def ^:private lex-list
(exec [_ (lex-str "(")
members lex-forms
_ (lex-str ")")]
(return [::list members])))
(def ^:private lex-tuple
(exec [_ (lex-str "[")
members lex-forms
_ (lex-str "]")]
(return [::tuple members])))
(def ^:private lex-record
(exec [_ (lex-str "{")
members lex-forms
_ (lex-str "}")]
(return [::record members])))
;; [Interface]
(defn lex [text]
(match (lex-forms 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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