48 case class CharParser(c: Char) extends Parser[String, Char] { |
48 case class CharParser(c: Char) extends Parser[String, Char] { |
49 def parse(in: String) = |
49 def parse(in: String) = |
50 if (in != "" && in.head == c) Set((c, in.tail)) else Set() |
50 if (in != "" && in.head == c) Set((c, in.tail)) else Set() |
51 } |
51 } |
52 |
52 |
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53 CharParser('c').parse("abc") |
53 |
54 |
54 // an atomic parser for parsing strings according to a regex |
55 // an atomic parser for parsing strings according to a regex |
55 import scala.util.matching.Regex |
56 import scala.util.matching.Regex |
56 |
57 |
57 case class RegexParser(reg: Regex) extends Parser[String, String] { |
58 case class RegexParser(reg: Regex) extends Parser[String, String] { |
63 |
64 |
64 // atomic parsers for numbers and "verbatim" strings |
65 // atomic parsers for numbers and "verbatim" strings |
65 val NumParser = RegexParser("[0-9]+".r) |
66 val NumParser = RegexParser("[0-9]+".r) |
66 def StrParser(s: String) = RegexParser(Regex.quote(s).r) |
67 def StrParser(s: String) = RegexParser(Regex.quote(s).r) |
67 |
68 |
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69 NumParser.parse("a123a123bc") |
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70 StrParser("else").parse("eelsethen") |
68 |
71 |
69 |
72 |
70 // NumParserInt transforms a "string integer" into a propper Int |
73 // NumParserInt transforms a "string integer" into a propper Int |
71 // (needs "new" because MapParser is not a case class) |
74 // (needs "new" because MapParser is not a case class) |
72 |
75 |
73 val NumParserInt = new MapParser(NumParser, (s: String) => s.toInt) |
76 val NumParserInt = new MapParser(NumParser, (s: String) => s.toInt) |
74 |
77 NumParserInt.parse("123abc") |
75 |
78 |
76 // the following string interpolation allows us to write |
79 // the following string interpolation allows us to write |
77 // StrParser(_some_string_) more conveniently as |
80 // StrParser(_some_string_) more conveniently as |
78 // |
81 // |
79 // p"<_some_string_>" |
82 // p"<_some_string_>" |
80 |
83 |
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84 |
81 implicit def parser_interpolation(sc: StringContext) = new { |
85 implicit def parser_interpolation(sc: StringContext) = new { |
82 def p(args: Any*) = StrParser(sc.s(args:_*)) |
86 def p(args: Any*) = StrParser(sc.s(args:_*)) |
83 } |
87 } |
84 |
88 |
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89 (p"else").parse("elsethen") |
85 |
90 |
86 // more convenient syntax for parser combinators |
91 // more convenient syntax for parser combinators |
87 implicit def ParserOps[I : IsSeq, T](p: Parser[I, T]) = new { |
92 implicit def ParserOps[I : IsSeq, T](p: Parser[I, T]) = new { |
88 def ||(q : => Parser[I, T]) = new AltParser[I, T](p, q) |
93 def ||(q : => Parser[I, T]) = new AltParser[I, T](p, q) |
89 def ~[S] (q : => Parser[I, S]) = new SeqParser[I, T, S](p, q) |
94 def ~[S] (q : => Parser[I, S]) = new SeqParser[I, T, S](p, q) |
90 def map[S](f: => T => S) = new MapParser[I, T, S](p, f) |
95 def map[S](f: => T => S) = new MapParser[I, T, S](p, f) |
91 } |
96 } |
92 |
97 |
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98 def toU(s: String) = s.map(_.toUpper) |
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99 |
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100 (p"ELSE").map(toU(_)).parse("ELSEifthen") |
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101 |
93 // these implicits allow us to use an infix notation for |
102 // these implicits allow us to use an infix notation for |
94 // sequences and alternatives; we also can write the usual |
103 // sequences and alternatives; we also can write the usual |
95 // map for a MapParser |
104 // map for a MapParser |
96 |
105 |
97 |
106 |
99 // as: |
108 // as: |
100 |
109 |
101 val NumParserInt2 = NumParser.map(_.toInt) |
110 val NumParserInt2 = NumParser.map(_.toInt) |
102 |
111 |
103 |
112 |
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113 |
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114 |
104 // A parser for palindromes (just returns them as string) |
115 // A parser for palindromes (just returns them as string) |
105 lazy val Pal : Parser[String, String] = { |
116 lazy val Pal : Parser[String, String] = { |
106 ((p"a" ~ Pal) ~ p"a").map{ case ((x, y), z) => s"$x$y$z" } || |
117 (p"a" ~ Pal ~ p"a").map{ case ((x, y), z) => s"$x$y$z" } || |
107 (p"b" ~ Pal ~ p"b").map{ case ((x, y), z) => s"$x$y$z" } || |
118 (p"b" ~ Pal ~ p"b").map{ case ((x, y), z) => s"$x$y$z" } || |
108 p"a" || p"b" || p"" |
119 p"a" || p"b" || p"" |
109 } |
120 } |
110 |
121 |
111 // examples |
122 // examples |
128 println(P.parse_all("(((()()))()))")) |
139 println(P.parse_all("(((()()))()))")) |
129 println(P.parse_all(")(")) |
140 println(P.parse_all(")(")) |
130 println(P.parse_all("()")) |
141 println(P.parse_all("()")) |
131 |
142 |
132 // A parser for arithmetic expressions (Terms and Factors) |
143 // A parser for arithmetic expressions (Terms and Factors) |
133 |
144 { |
134 lazy val E: Parser[String, Int] = { |
145 lazy val E: Parser[String, Int] = { |
135 (T ~ p"+" ~ E).map{ case ((x, _), z) => x + z } || |
146 (T ~ p"+" ~ E).map{ case ((x, _), z) => x + z } || |
136 (T ~ p"-" ~ E).map{ case ((x, _), z) => x - z } || T } |
147 (T ~ p"-" ~ E).map{ case ((x, _), z) => x - z } || T } |
137 lazy val T: Parser[String, Int] = { |
148 lazy val T: Parser[String, Int] = { |
138 (F ~ p"*" ~ T).map{ case ((x, _), z) => x * z } || F } |
149 (F ~ p"*" ~ T).map{ case ((x, _), z) => x * z } || F } |
139 lazy val F: Parser[String, Int] = { |
150 lazy val F: Parser[String, Int] = { |
140 (p"(" ~ E ~ p")").map{ case ((_, y), _) => y } || NumParserInt } |
151 (p"(" ~ E ~ p")").map{ case ((_, y), _) => y } || NumParserInt } |
141 |
152 } |
142 println(E.parse_all("1+3+4")) |
153 println(E.parse_all("1+3+4")) |
143 println(E.parse("1+3+4")) |
154 println(E.parse("1+3+4")) |
144 println(E.parse_all("4*2+3")) |
155 println(E.parse_all("4*2+3")) |
145 println(E.parse_all("4*(2+3)")) |
156 println(E.parse_all("4*(2+3)")) |
146 println(E.parse_all("(4)*((2+3))")) |
157 println(E.parse_all("(4)*((2+3))")) |