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+--1 The GF Prelude
+
+-- This file defines some prelude facilities usable in all grammars.
+
+resource Prelude = open (Predef=Predef) in {
+
+oper
+
+--2 Strings, records, and tables
+
+  SS  : Type = {s : Str} ;
+  ss  : Str -> SS = \s -> {s = s} ;
+  ss2 : (_,_ : Str) -> SS = \x,y -> ss (x ++ y) ;
+  ss3 : (_,_ ,_: Str) -> SS = \x,y,z -> ss (x ++ y ++ z) ;
+
+  cc2 : (_,_ : SS) -> SS = \x,y -> ss (x.s ++ y.s) ;
+  cc3 : (_,_,_ : SS) -> SS = \x,y,z -> ss (x.s ++ y.s ++ z.s) ;
+
+  SS1 : Type -> Type = \P -> {s : P => Str} ;
+  ss1 : (A : Type) -> Str -> SS1 A = \A,s -> {s = table {_ => s}} ;
+
+  SP1 : Type -> Type = \P -> {s : Str ; p : P} ;
+  sp1 : (A : Type) -> Str -> A -> SP1 A = \_,s,a -> {s = s ; p = a} ;
+
+  constTable : (A,B : Type) -> B -> A => B = \_,_,b -> \\_ => b ;
+  constStr   : (A : Type) -> Str -> A => Str = \A -> constTable A Str ;
+
+-- Discontinuous constituents.
+
+  SD2 : Type = {s1,s2 : Str} ;
+  sd2 : (_,_ : Str) -> SD2 = \x,y -> {s1 = x ; s2 = y} ;
+
+
+--2 Optional elements
+
+-- Missing form.
+
+  nonExist : Str = variants {} ;
+
+-- Optional string with preference on the string vs. empty.
+ 
+  optStr : Str -> Str = \s -> variants {s ; []} ;
+  strOpt : Str -> Str = \s -> variants {[] ; s} ;
+
+-- Free order between two strings.
+
+  bothWays : Str -> Str -> Str = \x,y -> variants {x ++ y ; y ++ x} ;
+
+-- Parametric order between two strings.
+
+  preOrPost : Bool -> Str -> Str -> Str = \pr,x,y -> 
+    if_then_Str pr (x ++ y) (y ++ x) ;
+
+--2 Infixes. prefixes, and postfixes
+
+-- Fixes with precedences are defined in [Precedence Precedence.html].
+
+  infixSS   : Str  -> SS -> SS -> SS = \f,x,y -> ss (x.s ++ f ++ y.s) ;
+  prefixSS  : Str        -> SS -> SS = \f,x   -> ss (f ++ x.s) ;
+  postfixSS : Str        -> SS -> SS = \f,x   -> ss (x.s ++ f) ;
+  embedSS   : Str -> Str -> SS -> SS = \f,g,x -> ss (f ++ x.s ++ g) ;
+
+
+--2 Booleans
+
+ param Bool = True | False ;
+
+oper
+  if_then_else : (A : Type) -> Bool -> A -> A -> A = \_,c,d,e -> 
+    case c of {
+      True => d ;  ---- should not need to qualify
+      False => e
+     } ;
+
+  andB : (_,_ : Bool) -> Bool = \a,b -> if_then_else Bool a b False ;
+  orB  : (_,_ : Bool) -> Bool = \a,b -> if_then_else Bool a True b ;
+  notB : Bool         -> Bool = \a   -> if_then_else Bool a False True ;
+
+  if_then_Str : Bool -> Str -> Str -> Str = if_then_else Str ;
+
+  onlyIf : Bool -> Str -> Str = \b,s -> case b of {
+    True => s ;
+    _ => nonExist
+    } ;
+
+-- Interface to internal booleans
+
+  pbool2bool : Predef.PBool -> Bool = \b -> case b of {
+    Predef.PFalse => False ; Predef.PTrue => True
+    } ;
+
+  init : Tok -> Tok = Predef.tk 1 ;
+  last : Tok -> Tok = Predef.dp 1 ;
+
+--2 High-level acces to Predef operations
+
+  isNil : Tok -> Bool = \b -> pbool2bool (Predef.eqStr [] b) ;
+
+  ifTok : (A : Type) -> Tok -> Tok -> A -> A -> A = \A,t,u,a,b -> 
+    case Predef.eqStr t u of {Predef.PTrue => a ; Predef.PFalse => b} ;
+
+--2 Lexer-related operations
+
+-- Bind together two tokens in some lexers, either obligatorily or optionally
+
+  oper 
+    glue : Str -> Str -> Str = \x,y -> x ++ BIND ++ y ;
+    glueOpt : Str -> Str -> Str = \x,y -> variants {glue x y ; x ++ y} ;
+    noglueOpt : Str -> Str -> Str = \x,y -> variants {x ++ y ; glue x y} ;
+
+-- Force capitalization of next word in some unlexers
+
+    capitalize : Str -> Str = \s -> CAPIT ++ s ;
+
+-- These should be hidden, and never changed since they are hardcoded in (un)lexers
+
+    BIND : Str = "&+" ;
+    PARA : Str = "&-" ;
+    CAPIT : Str = "&|" ;
+
+--2 Miscellaneous
+
+-- Identity function
+
+  id : (A : Type) -> A -> A = \_,a -> a ;
+
+-- Parentheses
+
+  paren : Str -> Str = \s -> "(" ++ s ++ ")" ;
+  parenss : SS -> SS = \s -> ss (paren s.s) ;
+
+-- Zero, one, two, or more (elements in a list etc)
+
+param
+  ENumber = E0 | E1 | E2 | Emore ;
+
+oper
+  eNext : ENumber -> ENumber = \e -> case e of {
+    E0 => E1 ; E1 => E2 ; _ => Emore} ;
+
+
+}