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new precedence lib

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aarne
2007-09-04 18:14:36 +00:00
parent 713fb9122c
commit 6150508b4e
1 changed files with 1 additions and 36 deletions
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37
examples/tutorial/calculator/CalculatorC.gf
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@@ -1,6 +1,6 @@
--# -path=.:prelude
concrete CalculatorC of Calculator = open Predef,Prelude in {
concrete CalculatorC of Calculator = open Prelude, Formal in {
flags lexer=codevars ; unlexer=code ;
@@ -21,39 +21,4 @@ concrete CalculatorC of Calculator = open Predef,Prelude in {
EInt i = constant i.s ;
EVar x = constant x.s ;
oper
Prec : PType = Ints 2 ;
TermPrec : Type = {s : Str ; p : Prec} ;
lessPrec : Prec -> Prec -> Bool = \p,q ->
case <<p,q> : Prec * Prec> of {
<1,1> | <1,0> | <0,0> => False ;
<1,_> | <0,_> => True ;
_ => False
} ;
usePrec : TermPrec -> Prec -> Str = \x,p ->
case lessPrec x.p p of {
True => paren x.s ;
False => noparen x.s
} ;
paren : Str -> Str = \s -> "(" ++ s ++ ")" ;
noparen : Str -> Str = \s -> variants {s ; "(" ++ s ++ ")"} ;
top : TermPrec -> Str = \t -> usePrec t 0 ;
mkPrec : Prec -> Str -> TermPrec = \p,s ->
{s = s ; p = p} ;
constant : Str -> TermPrec = mkPrec 2 ;
infixl : Prec -> Str -> (_,_ : TermPrec) -> TermPrec = \p,f,x,y ->
mkPrec p (usePrec x p ++ f ++ usePrec y (nextPrec p)) ;
nextPrec : Prec -> Prec = \p -> case <p : Prec> of {
2 => 2 ;
n => plus n 1
} ;
}