1 |
1 |
2 //:load matcher.scala |
2 //:load matcher.scala |
|
3 //:load parser3.scala |
3 |
4 |
4 // some regular expressions |
5 // some regular expressions |
5 val SYM = RANGE("""ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz_""") |
6 val SYM = RANGE("ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz_") |
6 val DIGIT = RANGE("0123456789") |
7 val DIGIT = RANGE("0123456789") |
7 val ID = SEQ(SYM, STAR(ALT(SYM, DIGIT))) |
8 val ID = SEQ(SYM, STAR(ALT(SYM, DIGIT))) |
8 val NUM = PLUS(DIGIT) |
9 val NUM = PLUS(DIGIT) |
9 val KEYWORD = ALTS("skip", "while", "do", "if", "then", "else", "begin", "end", "true", "false") |
10 val KEYWORD = ALTS("skip", "while", "do", "if", "then", "else", "true", "false") |
10 val SEMI: Rexp = ";" |
11 val SEMI: Rexp = ";" |
11 val OP: Rexp = ALTS(":=", "=", "+", "-", "*") |
12 val OP: Rexp = ALTS(":=", "=", "+", "-", "*") |
12 val WHITESPACE = PLUS(RANGE(" \n")) |
13 val WHITESPACE = PLUS(RANGE(" \n")) |
13 val RPAREN: Rexp = ")" |
14 val RPAREN: Rexp = ")" |
14 val LPAREN: Rexp = "(" |
15 val LPAREN: Rexp = "(" |
15 val BEGIN: Rexp = "{" |
16 val BEGIN: Rexp = "{" |
16 val END: Rexp = "}" |
17 val END: Rexp = "}" |
17 |
18 |
18 // for classifying the strings that have been recognised |
19 // tokens for classifying the strings that have been recognised |
19 abstract class Token |
20 abstract class Token |
20 case object T_WHITESPACE extends Token |
21 case object T_WHITESPACE extends Token |
21 case object T_SEMI extends Token |
22 case object T_SEMI extends Token |
22 case object T_LPAREN extends Token |
23 case object T_LPAREN extends Token |
23 case object T_RPAREN extends Token |
24 case object T_RPAREN extends Token |
25 case object T_END extends Token |
26 case object T_END extends Token |
26 case class T_ID(s: String) extends Token |
27 case class T_ID(s: String) extends Token |
27 case class T_OP(s: String) extends Token |
28 case class T_OP(s: String) extends Token |
28 case class T_NUM(s: String) extends Token |
29 case class T_NUM(s: String) extends Token |
29 case class T_KWD(s: String) extends Token |
30 case class T_KWD(s: String) extends Token |
30 |
|
31 |
31 |
32 val lexing_rules: List[Rule[Token]] = |
32 val lexing_rules: List[Rule[Token]] = |
33 List((KEYWORD, (s) => T_KWD(s.mkString)), |
33 List((KEYWORD, (s) => T_KWD(s.mkString)), |
34 (ID, (s) => T_ID(s.mkString)), |
34 (ID, (s) => T_ID(s.mkString)), |
35 (OP, (s) => T_OP(s.mkString)), |
35 (OP, (s) => T_OP(s.mkString)), |
51 type Block = List[Stmt] |
51 type Block = List[Stmt] |
52 case object Skip extends Stmt |
52 case object Skip extends Stmt |
53 case class If(a: BExp, bl1: Block, bl2: Block) extends Stmt |
53 case class If(a: BExp, bl1: Block, bl2: Block) extends Stmt |
54 case class While(b: BExp, bl: Block) extends Stmt |
54 case class While(b: BExp, bl: Block) extends Stmt |
55 case class Assign(s: String, a: AExp) extends Stmt |
55 case class Assign(s: String, a: AExp) extends Stmt |
|
56 |
56 case class Var(s: String) extends AExp |
57 case class Var(s: String) extends AExp |
57 case class Num(i: Int) extends AExp |
58 case class Num(i: Int) extends AExp |
58 case class Aop(o: String, a1: AExp, a2: AExp) extends AExp |
59 case class Aop(o: String, a1: AExp, a2: AExp) extends AExp |
|
60 |
59 case object True extends BExp |
61 case object True extends BExp |
60 case object False extends BExp |
62 case object False extends BExp |
61 case class Bop(o: String, a1: AExp, a2: AExp) extends BExp |
63 case class Bop(o: String, a1: AExp, a2: AExp) extends BExp |
62 |
64 |
63 |
65 // atomic parsers |
64 case class TokParser(tok: Token) extends Parser[List[Token], Token] { |
66 case class TokParser(tok: Token) extends Parser[List[Token], Token] { |
65 def parse(ts: List[Token]) = ts match { |
67 def parse(ts: List[Token]) = ts match { |
66 case t::ts if (t == tok) => Set((t, ts)) |
68 case t::ts if (t == tok) => Set((t, ts)) |
67 case _ => Set () |
69 case _ => Set () |
68 } |
70 } |
89 (T ~ T_OP("-") ~ AExp) ==> { case ((x, y), z) => Aop("-", x, z): AExp } || T |
91 (T ~ T_OP("-") ~ AExp) ==> { case ((x, y), z) => Aop("-", x, z): AExp } || T |
90 lazy val T: Parser[List[Token], AExp] = |
92 lazy val T: Parser[List[Token], AExp] = |
91 (F ~ T_OP("*") ~ T) ==> { case ((x, y), z) => Aop("*", x, z): AExp } || F |
93 (F ~ T_OP("*") ~ T) ==> { case ((x, y), z) => Aop("*", x, z): AExp } || F |
92 lazy val F: Parser[List[Token], AExp] = |
94 lazy val F: Parser[List[Token], AExp] = |
93 (T_LPAREN ~> AExp <~ T_RPAREN) || |
95 (T_LPAREN ~> AExp <~ T_RPAREN) || |
94 IdParser ==> ((s) => Var(s)) || |
96 IdParser ==> Var || |
95 NumParser ==> ((i) => Num(i)) |
97 NumParser ==> Num |
96 |
98 |
97 lazy val BExp: Parser[List[Token], BExp] = |
99 lazy val BExp: Parser[List[Token], BExp] = |
98 (AExp ~ T_OP("=") ~ AExp) ==> { case ((x, y), z) => Bop("=", x, z): BExp } || |
100 (AExp ~ T_OP("=") ~ AExp) ==> { case ((x, y), z) => Bop("=", x, z): BExp } || |
99 (T_KWD("true") ==> ((_) => True: BExp)) || |
101 (T_KWD("true") ==> ((_) => True)) || |
100 (T_KWD("false") ==> ((_) => False: BExp)) |
102 (T_KWD("false") ==> ((_) => False: BExp)) |
101 |
103 |
102 lazy val Stmt: Parser[List[Token], Stmt] = |
104 lazy val Stmt: Parser[List[Token], Stmt] = |
103 (T_KWD("skip") ==> ((_) => Skip: Stmt)) || |
105 (T_KWD("skip") ==> ((_) => Skip: Stmt)) || |
104 (IdParser ~ T_OP(":=") ~ AExp) ==> { case ((x, y), z) => Assign(x, z): Stmt } || |
106 (IdParser ~ T_OP(":=") ~ AExp) ==> { case ((x, y), z) => Assign(x, z): Stmt } || |
111 |
113 |
112 lazy val Block: Parser[List[Token], Block] = |
114 lazy val Block: Parser[List[Token], Block] = |
113 (T_BEGIN ~> Stmts <~ T_END) || |
115 (T_BEGIN ~> Stmts <~ T_END) || |
114 (Stmt ==> ((s) => List(s))) |
116 (Stmt ==> ((s) => List(s))) |
115 |
117 |
|
118 |
|
119 // examples |
116 val p1 = "x := 5" |
120 val p1 = "x := 5" |
117 val p1_toks = Tok.fromString(p1) |
121 val p1_toks = Tok.fromString(p1) |
118 val p1_ast = Block.parse_all(p1_toks) |
122 val p1_ast = Block.parse_all(p1_toks) |
119 println(p1_toks) |
123 println(p1_toks) |
120 println(p1_ast) |
124 println(p1_ast) |
121 |
125 |
|
126 val p1a = "{ x := 5; y := 8}" |
|
127 val p1a_toks = Tok.fromString(p1a) |
|
128 val p1a_ast = Block.parse_all(p1a_toks) |
|
129 println(p1a_ast) |
|
130 |
122 val p2 = "5 = 6" |
131 val p2 = "5 = 6" |
123 val p2_toks = Tok.fromString(p2) |
132 val p2_toks = Tok.fromString(p2) |
124 val p2_ast = BExp.parse_all(p2_toks) |
133 val p2_ast = BExp.parse_all(p2_toks) |
125 println(p2_toks) |
|
126 println(p2_ast) |
134 println(p2_ast) |
127 |
135 |
128 val p2a = "true" |
136 val p2a = "true" |
129 val p2a_toks = Tok.fromString(p2a) |
137 val p2a_toks = Tok.fromString(p2a) |
130 val p2a_ast = BExp.parse_all(p2a_toks) |
138 val p2a_ast = BExp.parse_all(p2a_toks) |
131 println(p2a_toks) |
|
132 println(p2a_ast) |
139 println(p2a_ast) |
133 |
140 |
134 val p3 = "if true then skip else skip" |
141 val p3 = "if true then skip else skip" |
135 val p3_toks = Tok.fromString(p3) |
142 val p3_toks = Tok.fromString(p3) |
136 val p3_ast = Stmt.parse_all(p3_toks) |
143 val p3_ast = Stmt.parse_all(p3_toks) |
137 println(p3_toks) |
|
138 println(p3_ast) |
144 println(p3_ast) |
139 |
145 |
140 val p3a = "if true then x := 5 else x := 10" |
146 val p3a = "if true then x := 5 else x := 10" |
141 val p3a_toks = Tok.fromString(p3a) |
147 val p3a_toks = Tok.fromString(p3a) |
142 val p3a_ast = Stmt.parse_all(p3a_toks) |
148 val p3a_ast = Stmt.parse_all(p3a_toks) |
143 println(p3a_toks) |
|
144 println(p3a_ast) |
149 println(p3a_ast) |
145 |
150 |
146 val p3b = "if false then x := 5 else x := 10" |
151 val p3b = "if false then x := 5 else x := 10" |
147 val p3b_toks = Tok.fromString(p3b) |
152 val p3b_toks = Tok.fromString(p3b) |
148 val p3b_ast = Stmt.parse_all(p3b_toks) |
153 val p3b_ast = Stmt.parse_all(p3b_toks) |
149 println(p3b_toks) |
|
150 println(p3b_ast) |
154 println(p3b_ast) |
151 |
155 |
|
156 val p4 = """{ x := 5; |
|
157 y := 3; |
|
158 r := 0; |
|
159 while y = 0 do { |
|
160 r := r + x; |
|
161 y := y - 1 |
|
162 } |
|
163 }""" |
|
164 val p4_toks = Tok.fromString(p4) |
|
165 val p4_ast = Block.parse_all(p4_toks) |
|
166 println(p4_ast) |
152 |
167 |
|
168 |
|
169 // interpreter |
153 type Env = Map[String, Int] |
170 type Env = Map[String, Int] |
154 |
171 |
155 def eval_bexp(b: BExp, env: Env) : Boolean = b match { |
172 def eval_bexp(b: BExp, env: Env) : Boolean = b match { |
156 case True => true |
173 case True => true |
157 case False => false |
174 case False => false |