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(ns cljcc.parser
(:require
[cljcc.lexer :as l]
[clojure.pprint :as pp]))
(defn- expect [expected-kind [token & rst]]
(if (= expected-kind (:kind token))
[token rst]
(throw (ex-info "Parser Error." {:expected expected-kind
:actual (:kind token)}))))
(defn- parse-exp [tokens]
(let [[t rst] (expect :number tokens)]
[{:type :exp
:value {:type :constant-exp
:value (:literal t)}} rst]))
(defn- parse-return-statement [tokens]
(let [[_ rst] (expect :kw-return tokens)
[constant-node rst] (parse-exp rst)]
[{:type :statement
:statement-type :return
:value constant-node}
rst]))
(defn- parse-statement
"Parses a single statement. Expects a semicolon at the end."
[[token :as tokens]]
(let [[statement rst]
(cond
(= (:kind token) :kw-return) (parse-return-statement tokens)
:else (throw (ex-info "Parser Error. Unexpected statement. " {:token token})))
[_ rst] (expect :semicolon rst)]
[statement rst]))
(defn- keyword->type [k]
(condp = k
:kw-int "int"
(throw (ex-info "Parser Error. Unsupported type." {:keyword k}))))
(defn- parse-function [tokens]
(let [[fn-type-token rst] (expect :kw-int tokens)
[fn-identifier-token rst] (expect :identifier rst)
[_ rst] (expect :left-paren rst)
[fn-parameter-token rst] (expect :kw-void rst)
[_ rst] (expect :right-paren rst)
[_ rst] (expect :left-curly rst)
[statement rst] (parse-statement rst)
[_ rst] (expect :right-curly rst)]
[{:type :function
:return-type (keyword->type (:kind fn-type-token))
:identifier (:literal fn-identifier-token)
:parameters (:kind fn-parameter-token)
:statements [statement]}
rst]))
(defn- parse-program [tokens]
(let [[ast rst] (parse-function tokens)
_ (expect :eof rst)]
[ast]))
(defn parse [tokens]
(-> tokens
:tokens
parse-program))
(comment
(parse "int main(void) {return 2;}")
(pp/pprint (parse (l/lex "
int main(void) {
return 2;
}")))
(pp/pprint
(l/lex "
int main(void) {
return 2;
}"))
(parse "int main(void) {
return -(((((10)))));
}")
(pp/pprint (parse "int main(void) {
return 1 & 2 + 6 & 6;
}"))
())
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