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(ns lux.lexer
(:require [clojure.template :refer [do-template]]
[lux.base :as & :refer [exec return* return fail fail*
repeat-m try-m try-all-m]]))
;; [Utils]
(defn ^:private lex-regex [regex]
(fn [state]
(if-let [[match] (re-find regex (::&/source state))]
(return* (update-in state [::&/source] #(.substring % (.length match))) match)
(fail* (str "[Lexer Error] Pattern failed: " regex)))))
(defn ^:private lex-regex2 [regex]
(fn [state]
(if-let [[match tok1 tok2] (re-find regex (::&/source state))]
(return* (update-in state [::&/source] #(.substring % (.length match))) [tok1 tok2])
(fail* (str "[Lexer Error] Pattern failed: " regex)))))
(defn ^:private lex-prefix [prefix]
(fn [state]
(if (.startsWith (::&/source state) prefix)
(return* (update-in state [::&/source] #(.substring % (.length prefix))) prefix)
(fail* (str "[Lexer Error] Text failed: " prefix)))))
(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 "[Lexer Error] Unknown escape character: " escaped))))
(def ^:private lex-text-body
(try-all-m [(exec [[prefix escaped] (lex-regex2 #"(?s)^([^\"\\]*)(\\.)")
unescaped (escape-char escaped)
postfix lex-text-body]
(return (str prefix unescaped postfix)))
(lex-regex #"(?s)^([^\"\\]*)")]))
(def ^:private +ident-re+ #"^([a-zA-Z\-\+\_\=!@$%^&*<>\.,/\\\|':\~\?][0-9a-zA-Z\-\+\_\=!@$%^&*<>\.,/\\\|':\~\?]*)(;[0-9a-zA-Z\-\+\_\=!@$%^&*<>\.,/\\\|':\~\?]+)?")
;; [Lexers]
(def ^:private lex-white-space
(exec [white-space (lex-regex #"^(\s+)")]
(return [::white-space white-space])))
(def ^:private lex-single-line-comment
(exec [_ (lex-prefix "##")
comment (lex-regex #"^([^\n]*)")
_ (lex-regex #"^(\n?)")]
(return [::comment comment])))
(def ^:private lex-multi-line-comment
(exec [_ (lex-prefix "#(")
comment (try-all-m [(lex-regex #"(?is)^((?!#\().)*?(?=\)#)")
(exec [pre (lex-regex #"(?is)^(.+?(?=#\())")
[_ inner] lex-multi-line-comment
post (lex-regex #"(?is)^(.+?(?=\)#))")]
(return (str pre "#(" inner ")#" post)))])
_ (lex-prefix ")#")]
(return [::comment comment])))
(def ^:private lex-comment
(try-all-m [lex-single-line-comment
lex-multi-line-comment]))
(do-template [<name> <tag> <regex>]
(def <name>
(exec [token (lex-regex <regex>)]
(return [<tag> token])))
^:private lex-bool ::bool #"^(true|false)"
^:private lex-real ::real #"^(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-prefix "#\"")
token (try-all-m [(exec [escaped (lex-regex #"^(\\.)")]
(escape-char escaped))
(lex-regex #"^(.)")])
_ (lex-prefix "\"")]
(return [::char token])))
(def ^:private lex-text
(exec [_ (lex-prefix "\"")
token lex-text-body
_ (lex-prefix "\"")]
(return [::text token])))
(def ^:private lex-tag
(exec [_ (lex-prefix "#")
token (lex-regex +ident-re+)]
(return [::tag token])))
(do-template [<name> <text> <tag>]
(def <name>
(exec [_ (lex-prefix <text>)]
(return [<tag>])))
^:private lex-open-paren "(" ::open-paren
^:private lex-close-paren ")" ::close-paren
^:private lex-open-bracket "[" ::open-bracket
^:private lex-close-bracket "]" ::close-bracket
^:private lex-open-brace "{" ::open-brace
^:private lex-close-brace "}" ::close-brace
)
(def ^:private lex-delimiter
(try-all-m [lex-open-paren
lex-close-paren
lex-open-bracket
lex-close-bracket
lex-open-brace
lex-close-brace]))
;; [Exports]
(def lex
(try-all-m [lex-white-space
lex-comment
lex-bool
lex-real
lex-int
lex-char
lex-text
lex-ident
lex-tag
lex-delimiter]))
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