Tigerインタプリタで条件分岐したい

やったこと

関数から返ってきた際に関数内の env をそのまま利用してしまうバグを修正

フィボナッチ数が計算できるようになった

code:diff

diff --git a/lib/eval.ml b/lib/eval.ml

index 7cb0bed..d759c21 100644

--- a/lib/eval.ml

+++ b/lib/eval.ml

@@ -17,6 +17,15 @@ let rec f expr env: val_t * table =

env

decs

in f body new_env

+ | Syntax.IfExp { test; then'; else' } ->

+ let v, env = f test env in

+ (match v with

+ | IntVal 1 -> f then' env

+ | IntVal 0 ->

+ (match else' with

+ | Some else' -> f else' env

+ | None -> (IntVal 0, env))

+ | _ -> failwith "type error")

| Syntax.CallExp { id; args } ->

(let func = List.assoc id env in

match func with

@@ -30,7 +39,8 @@ let rec f expr env: val_t * table =

| _ -> failwith "type error"

in

let new_env = get_args args env field_names in

- f body new_env

+ let result, _ = f body new_env

+ in result, env

| BuiltInFunction builtin_func ->

(let rec eval_args args env =

match args with

diff --git a/lib/lexer.mll b/lib/lexer.mll

index 2c651ef..8031094 100644

--- a/lib/lexer.mll

+++ b/lib/lexer.mll

@@ -19,6 +19,9 @@ rule token = parse

| "end" { Parser.END }

| "var" { Parser.VAR }

| "function" { Parser.FUNCTION }

+ | "if" { Parser.IF }

+ | "then" { Parser.THEN }

+ | "else" { Parser.ELSE }

| "+" { Parser.PLUS }

| "-" { Parser.MINUS }

| "*" { Parser.TIMES }

diff --git a/lib/parser.mly b/lib/parser.mly

index df68faa..fa74fa2 100644

--- a/lib/parser.mly

+++ b/lib/parser.mly

@@ -8,7 +8,7 @@

%token <string> ID

%token PLUS MINUS TIMES DIVIDE

%token EQ NEQ LT LE GT GE

-%token LET IN END

+%token LET IN END IF THEN ELSE

%token VAR FUNCTION ASSIGN

%token LPAREN RPAREN COMMA COLON

%token EOF

@@ -17,7 +17,7 @@

// %token COMMA COLON SEMICOLON LPAREN RPAREN LBRACK RBRACK

// %token LBRACE RBRACE DOT

// %token AND OR

-// %token ARRAY IF THEN ELSE WHILE FOR TO DO OF

+// %token ARRAY WHILE FOR TO DO OF

// %token BREAK NIL

// %token FUNCTION TYPE

@@ -38,6 +38,7 @@ exp:

INT { Syntax.IntExp($1) }

| STRING { Syntax.StringExp($1) }

| ID { Syntax.VarExp($1) }

+| LPAREN exp RPAREN { $2 }

| exp PLUS exp { Syntax.OpExp { left = $1; op = Syntax.PlusOp; right = $3} }

| exp MINUS exp { Syntax.OpExp { left = $1; op = Syntax.MinusOp; right = $3} }

| exp TIMES exp { Syntax.OpExp { left = $1; op = Syntax.TimesOp; right = $3} }

@@ -50,6 +51,8 @@ exp:

| exp GE exp { Syntax.OpExp { left = $1; op = Syntax.GeOp; right = $3} }

| LET decs IN exp END { Syntax.LetExp { decs = $2; body = $4 } }

| ID LPAREN args RPAREN { Syntax.CallExp { id = $1; args = $3 } }

+| IF exp THEN exp { Syntax.IfExp { test = $2; then' = $4; else' = None } }

+| IF exp THEN exp ELSE exp { Syntax.IfExp { test = $2; then' = $4; else' = Some ($6) } }

args:

{ [] } // 空の場合

diff --git a/lib/syntax.ml b/lib/syntax.ml

index f01250b..fdbabc8 100644

--- a/lib/syntax.ml

+++ b/lib/syntax.ml

@@ -19,6 +19,7 @@ and op_t =

| VarExp of string

| CallExp of { id: string; args: t list } (* 関数呼び出し *)

| OpExp of { left: t; op: op_t; right: t } (* 二項演算子 *)

+ | IfExp of { test: t; then': t; else': t option } (* if文 *)

and dec_t =

| VarDec of symbol * t (* 変数宣言 *)

diff --git a/samples/fib.tiger b/samples/fib.tiger

new file mode 100644

index 0000000..8fba652

--- /dev/null

+++ b/samples/fib.tiger

@@ -0,0 +1,7 @@

+let

+ function fib(n:int) =

+ if n < 2 then n

+ else fib(n-1) + fib(n-2)

+in

+ fib(10)

+end

diff --git a/test/tiger_test.expected b/test/tiger_test.expected

index aac8ff3..f44e0a3 100644

--- a/test/tiger_test.expected

+++ b/test/tiger_test.expected

@@ -28,3 +28,5 @@ result: 100

result: 20

result: 4649

Hello World!!

+Goodbye World!!

+result: 55

diff --git a/test/tiger_test.ml b/test/tiger_test.ml

index 3ada260..ea6f020 100644

--- a/test/tiger_test.ml

+++ b/test/tiger_test.ml

@@ -267,13 +267,38 @@ let () =

Tiger.Eval.print_val (eval_with_env src env);

print_newline ()

-(* 組み込み関数 print(s: string) の呼び出し *)

+(* if-then *)

let () =

let src = {|

let in

- print("Hello World!!")

+ if 1 = 1 then print("Hello World!!\n")

end

|}

in

- ignore(eval src);

+ ignore(eval src)

+

+(* if-then-else *)

+let () =

+ let src = {|

+ let in

+ if 1 = 0 then print("Hello World!!\n")

+ else print("Goodbye World!!\n")

+ end

+ |}

+ in

+ ignore(eval src)

+

+(* フィボナッチ数 *)

+let () =

+ let src = {|

+ let

+ function fib(n:int) =

+ if n < 2 then n

+ else fib(n-1) + fib(n-2)

+ in

+ fib(10)

+ end

+ |}

+ in print_string "result: ";

+ Tiger.Eval.print_val (eval src);

print_newline ()

yaccのコンフリクトの解消法

code:diff

diff --git a/lib/parser.mly b/lib/parser.mly

index fa74fa2..4040da7 100644

--- a/lib/parser.mly

+++ b/lib/parser.mly

@@ -26,9 +26,12 @@

%type <Syntax.t> program

-%left EQ NEQ LT LE GT GE

+%nonassoc THEN

+%nonassoc ELSE

%left PLUS MINUS

%left TIMES DIVIDE

+%nonassoc EQ NEQ LT LE GT GE

// 文法規則の定義

%%