pretty printing

lib/forgejo.ballcloud.cc/wball/proof-checker/FORMULA.sig

@@ -20,4 +20,7 @@ sig
   val matchVariable: int -> t * t -> Term.t option
 
   val occurs: Term.t -> t -> bool
+
+  val ppd: int -> int -> t -> string
+  val pp: t -> string
 end

lib/forgejo.ballcloud.cc/wball/proof-checker/Formula.sml

@@ -75,18 +75,63 @@ struct
     | matchVariable x (Iff (phi, psi), Iff (phi', psi')) =
         Term.mergeOption
           (matchVariable x (phi, phi'), matchVariable x (psi, psi'))
-    | matchVariable x (Exists phi, Exists psi) = matchVariable (x + 1) (phi, psi)
+    | matchVariable x (Exists phi, Exists psi) =
-    | matchVariable x (Forall phi, Forall psi) = matchVariable (x + 1) (phi, psi)
+        matchVariable (x + 1) (phi, psi)
+    | matchVariable x (Forall phi, Forall psi) =
+        matchVariable (x + 1) (phi, psi)
     | matchVariable _ _ = raise MatchFailure
 
-  fun occurs t (Relation (_, ts)) = List.exists (Term.occurs t) ts
+  fun occurs t (Relation (_, ts)) =
-    | occurs t (Equal (p, q)) = Term.occurs t p orelse Term.occurs t q
+        List.exists (Term.occurs t) ts
+    | occurs t (Equal (p, q)) =
+        Term.occurs t p orelse Term.occurs t q
     | occurs t Bottom = false
     | occurs t (Neg phi) = occurs t phi
-    | occurs t (Conj (phi, psi)) = occurs t phi orelse occurs t psi
+    | occurs t (Conj (phi, psi)) =
-    | occurs t (Disj (phi, psi)) = occurs t phi orelse occurs t psi
+        occurs t phi orelse occurs t psi
-    | occurs t (Impl (phi, psi)) = occurs t phi orelse occurs t psi
+    | occurs t (Disj (phi, psi)) =
-    | occurs t (Iff (phi, psi)) = occurs t phi orelse occurs t psi
+        occurs t phi orelse occurs t psi
-    | occurs t (Exists phi) = occurs (Term.incVars t) phi
+    | occurs t (Impl (phi, psi)) =
-    | occurs t (Forall phi) = occurs (Term.incVars t) phi
+        occurs t phi orelse occurs t psi
+    | occurs t (Iff (phi, psi)) =
+        occurs t phi orelse occurs t psi
+    | occurs t (Exists phi) =
+        occurs (Term.incVars t) phi
+    | occurs t (Forall phi) =
+        occurs (Term.incVars t) phi
+
+  val precedence =
+    fn Bottom => 10
+     | Relation _ => 10
+     | Equal _ => 10
+     | Neg _ => 9
+     | Conj _ => 8
+     | Disj _ => 7
+     | Impl _ => 6
+     | Iff _ => 5
+     | Forall _ => 4
+     | Exists _ => 4
+
+  fun ppd d prec prop =
+    let
+      val np = precedence prop
+      val str =
+        case prop of
+          Bottom => "\226\138\165"
+        | Relation (f, args) =>
+            f ^ "(" ^ (String.concatWith ", " (map (Term.ppd d) args)) ^ ")"
+        | Equal (t, s) => Term.ppd d t ^ " = " ^ Term.ppd d s
+        | Neg (Equal (t, s)) => Term.ppd d t ^ " != " ^ Term.ppd d s
+        | Neg phi => "~" ^ ppd d np phi
+        | Conj (phi, psi) => ppd d np phi ^ " \226\136\167 " ^ ppd d np psi
+        | Disj (phi, psi) => ppd d np phi ^ " \226\136\168 " ^ ppd d np psi
+        | Impl (phi, psi) => ppd d np phi ^ " => " ^ ppd d np psi
+        | Iff (phi, psi) => ppd d np phi ^ " <=> " ^ ppd d np psi
+        | Forall phi => "\226\136\128" ^ Var.name d ^ ". " ^ ppd (d + 1) np phi
+        | Exists phi => "\226\136\131" ^ Var.name d ^ ". " ^ ppd (d + 1) np phi
+    in
+      if np < prec then "(" ^ str ^ ")" else str
+    end
+
+  val pp = ppd 0 0
 end

lib/forgejo.ballcloud.cc/wball/proof-checker/Proof.sml

@@ -20,7 +20,7 @@ struct
   | ExistsI
   | ExistsE
 
-  exception ProofError of int
+  exception ProofError of string
 
   datatype t = Proof of {children: t list, label: label, formula: Formula.t}
 
@@ -209,8 +209,7 @@ struct
            | _ => false handle MatchFailure => false)
       | valid
           ( Proof
-          { children =
+              { children = [kid as Proof {formula = Exists phi, ...}]
-              [ kid as Proof {formula = Exists phi, ...} ]
               , label = ExistsE
               , formula = psi
               }

lib/forgejo.ballcloud.cc/wball/proof-checker/TERM.sig

@@ -18,4 +18,8 @@ sig
   val incVars: t -> t
 
   val occurs: t -> t -> bool
+
+  val ppd: int -> t -> string
+
+  val pp: t -> string
 end

lib/forgejo.ballcloud.cc/wball/proof-checker/Term.sml

@@ -46,16 +46,33 @@ struct
     | matchVariable x (Function (f, ts), Function (g, ss)) =
         foldl mergeOption NONE (map (matchVariable x)
           (ListPair.zipEq (ts, ss) handle UnequalLengths => raise MatchFailure))
-    | matchVariable _ (Free s1, Free s2) = if s1 = s2 then NONE else raise MatchFailure
+    | matchVariable _ (Free s1, Free s2) =
+        if s1 = s2 then NONE else raise MatchFailure
     | matchVariable _ _ = raise MatchFailure
 
-  fun incVars (Var x) = Var (x + 1)
+  fun incVars (Var x) =
-    | incVars (Function (f, args)) = Function (f, map incVars args)
+        Var (x + 1)
+    | incVars (Function (f, args)) =
+        Function (f, map incVars args)
     | incVars t = t
 
   fun occurs (Const s1) (Const s2) = s1 = s2
     | occurs (Var x1) (Var x2) = x1 = x2
-    | occurs t (Function (_, ts)) = List.exists (occurs t) ts
+    | occurs t (Function (_, ts)) =
+        List.exists (occurs t) ts
     | occurs (Free s1) (Free s2) = s1 = s2
     | occurs _ _ = false
+
+  fun ppd depth (Const s) = s
+    | ppd depth (Free s) = s
+    | ppd depth (Var x) =
+        Var.name (depth - x - 1)
+    | ppd depth (Function (f, x :: rest)) =
+        f ^ "("
+        ^
+        (foldl (fn (s, acc) => acc ^ ", " ^ s) (ppd depth x)
+           (map (ppd depth) rest)) ^ ")"
+    | ppd depth (Function (f, [])) = f ^ "()"
+
+  val pp = ppd 0
 end

lib/forgejo.ballcloud.cc/wball/proof-checker/VAR.sig

@@ -0,0 +1,4 @@
+signature VAR =
+sig
+  val name: int -> string
+end

lib/forgejo.ballcloud.cc/wball/proof-checker/Var.sml

@@ -0,0 +1,6 @@
+structure Var: VAR =
+struct
+  val name_list = ["x", "y", "z", "w", "u", "v"]
+  fun name x =
+    if x < 6 then List.nth (name_list, x) else "x" ^ Int.toString (x - 6)
+end

lib/forgejo.ballcloud.cc/wball/proof-checker/proof-checker.mlb

@@ -1,6 +1,8 @@
 $(SML_LIB)/basis/basis.mlb
 ../../../github.com/diku-dk/sml-parse/parse.mlb
 ../../../github.com/diku-dk/sml-parse/simple_token.mlb
+VAR.sig
+Var.sml
 TERM.sig
 Term.sml
 FORMULA.sig