53 lines
1.6 KiB
Scala
53 lines
1.6 KiB
Scala
package examples.parsing
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import scala.util.parsing.combinator1.syntactical.StandardTokenParsers
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import scala.util.parsing.combinator1.syntactical.StandardTokenParsers
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object MiniML extends StandardTokenParsers {
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lexical.delimiters += ("(", ")", ".", "=")
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lexical.reserved += ("lambda", "let", "in")
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def expr: Parser[Any] = (
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"let" ~ ident ~ "=" ~ expr ~ "in" ~ expr
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| "lambda" ~ ident ~ "." ~ expr
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| simpleExpr ~ rep(expr)
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)
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def simpleExpr: Parser[Any] = (
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ident
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| "(" ~ expr ~ ")"
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)
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def main(args: Array[String]) {
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val tokens = new lexical.Scanner(args(0))
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println(args(0))
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println(phrase(expr)(tokens))
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}
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}
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class Expr
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case class Let(x: String, expr: Expr, body: Expr) extends Expr
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case class Lambda(x: String, expr: Expr) extends Expr
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case class Apply(fun: Expr, arg: Expr) extends Expr
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case class Var(x: String) extends Expr
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object MiniML1 extends StandardTokenParsers {
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lexical.delimiters += ("(", ")", ".", "=")
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lexical.reserved += ("lambda", "let", "in")
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def expr: Parser[Expr] = (
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"let" ~ ident ~ "=" ~ expr ~ "in" ~ expr ^^ { case "let" ~ x ~ "=" ~ e ~ "in" ~ b => Let(x, e, b) }
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| "lambda" ~ ident ~ "." ~ expr ^^ { case "lambda" ~ x ~ "." ~ e => Lambda(x, e) }
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| simpleExpr ~ rep(expr) ^^ { case f ~ as => (f /: as) (Apply) }
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)
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def simpleExpr: Parser[Expr] = (
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ident ^^ { Var }
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| "(" ~> expr <~ ")"
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)
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def main(args: Array[String]) {
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val tokens = new lexical.Scanner(args(0))
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println(args(0))
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println(phrase(expr)(tokens))
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}
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}
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