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(ns step2-eval
(:require [clojure.repl]
[readline]
[reader]
[printer]))
;; read
(defn READ [& [strng]]
(let [line (if strng strng (read-line))]
(reader/read-string strng)))
;; eval
(declare EVAL)
(defn eval-ast [ast env]
(cond
(symbol? ast) (or (get env ast)
(throw (Error. (str ast " not found"))))
(seq? ast) (doall (map #(EVAL % env) ast))
(vector? ast) (vec (doall (map #(EVAL % env) ast)))
(map? ast) (apply hash-map (doall (map #(EVAL % env)
(mapcat identity ast))))
:else ast))
(defn EVAL [ast env]
;;(prn "EVAL" ast (keys @env)) (flush)
(if (not (seq? ast))
(eval-ast ast env)
;; apply list
(let [el (eval-ast ast env)
f (first el)
args (rest el)]
(apply f args))))
;; print
(defn PRINT [exp] (pr-str exp))
;; repl
(def repl-env {'+ +
'- -
'* *
'/ /})
(defn rep
[strng]
(PRINT (EVAL (READ strng) repl-env)))
;; repl loop
(defn repl-loop []
(let [line (readline/readline "user> ")]
(when line
(when-not (re-seq #"^\s*$|^\s*;.*$" line) ; blank/comment
(try
(println (rep line))
(catch Throwable e
(clojure.repl/pst e))))
(recur))))
(defn -main [& args]
(repl-loop))
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