fixes for issues #185 and #181

Cargo.toml

@@ -18,7 +18,7 @@ lazy_static = "1.4.0"
 libc = "0.2.62"
 nix = "0.15.0"
 ordered-float = "0.5.0"
-prolog_parser = "0.8.31"
+prolog_parser = "0.8.32"
 ref_thread_local = "0.0.0"
 rug = "1.4.0"
 rustyline = "5.0.3"

src/prolog/clause_types.rs

@@ -542,10 +542,10 @@ impl ClauseType {
         match self {
             &ClauseType::Op(_, ref spec, _) => Some(spec.clone()),
             &ClauseType::Inlined(InlinedClauseType::CompareNumber(..))
-            | &ClauseType::BuiltIn(BuiltInClauseType::Is(..))
-            | &ClauseType::BuiltIn(BuiltInClauseType::CompareTerm(_))
-            | &ClauseType::BuiltIn(BuiltInClauseType::NotEq)
-            | &ClauseType::BuiltIn(BuiltInClauseType::Eq) => Some(SharedOpDesc::new(700, XFX)),
+          | &ClauseType::BuiltIn(BuiltInClauseType::Is(..))
+          | &ClauseType::BuiltIn(BuiltInClauseType::CompareTerm(_))
+          | &ClauseType::BuiltIn(BuiltInClauseType::NotEq)
+          | &ClauseType::BuiltIn(BuiltInClauseType::Eq) => Some(SharedOpDesc::new(700, XFX)),
             _ => None,
         }
     }

src/prolog/forms.rs

@@ -280,6 +280,15 @@ pub fn fetch_op_spec(
     spec: Option<SharedOpDesc>,
     op_dir: &OpDir,
 ) -> Option<SharedOpDesc> {
+    if let Some(ref op_desc) = &spec {
+        if op_desc.arity() != arity {            
+            /* it's possible to extend operator functors with
+             * additional terms. When that happens,
+             * void the op_spec by returning None. */
+            return None; 
+        }
+    }
+
     spec.or_else(|| match arity {
         2 => op_dir
             .get(&(name, Fixity::In))

src/prolog/heap_print.rs

@@ -922,7 +922,9 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
         match heap_val {
             HeapCellValue::NamedStr(arity, name, spec) => {
-                if let Some(spec) = fetch_op_spec(name.clone(), arity, spec.clone(), self.op_dir) {
+                let spec = fetch_op_spec(name.clone(), arity, spec.clone(), self.op_dir);
+                
+                if let Some(spec) = spec {
                     self.handle_op_as_struct(
                         name,
                         arity,

src/prolog/machine/machine_state_impl.rs

@@ -1114,7 +1114,7 @@ impl MachineState {
     }
 
     fn pow(&self, n1: Number, n2: Number, culprit: &'static str) -> Result<Number, MachineStub> {
-        if n2.is_negative() {
+        if n2.is_negative() && n1.is_zero() {
             let stub = MachineError::functor_stub(clause_name!(culprit), 2);
             return Err(self.error_form(MachineError::evaluation_error(EvalError::Undefined), stub));
         }

src/prolog/toplevel.pl

@@ -31,13 +31,9 @@
     !.
 
 '$print_exception'(E) :-
-    (  E = error(_, _:_) -> true % if the error source contains a line
-                                 % number, a GNU-style error message
-                                 % is expected to be printed instead.
-    ;  write_term('caught: ', [quoted(false)]),
-       writeq(E),
-       nl
-    ).
+    write_term('caught: ', [quoted(false)]),
+    writeq(E),
+    nl.    
 
 '$predicate_indicator'(Source, PI) :-
     (  nonvar(PI) ->