quote solo characters wherever they lead atoms

Cargo.toml

@@ -12,6 +12,7 @@ default = ["readline_rs_compat"]
 [dependencies]
 cfg-if = "0.1.7"
 downcast = "0.10.0"
+indexmap = "1.0.2"
 num = "0.2"
 ordered-float = "0.5.0"
 prolog_parser = "0.8.26"

src/main.rs

@@ -1,5 +1,6 @@
 #[macro_use] extern crate cfg_if;
 #[macro_use] extern crate downcast;
+extern crate indexmap;
 #[macro_use] extern crate prolog_parser;
 #[macro_use] extern crate ref_thread_local;
 

src/prolog/debray_allocator.rs

@@ -1,3 +1,5 @@
+use indexmap::IndexMap;
+
 use prolog_parser::ast::*;
 
 use prolog::allocator::*;
@@ -11,7 +13,7 @@ use std::collections::{BTreeSet, HashMap};
 use std::rc::Rc;
 
 pub struct DebrayAllocator {
-    bindings: HashMap<Rc<Var>, VarData>,
+    bindings: IndexMap<Rc<Var>, VarData>,
     arg_c:    usize,
     temp_lb:  usize,
     arity:    usize, // 0 if not at head.
@@ -207,7 +209,7 @@ impl<'a> Allocator<'a> for DebrayAllocator
             arity:   0,
             arg_c:   1,
             temp_lb: 1,
-            bindings: HashMap::new(),
+            bindings: IndexMap::new(),
             contents: HashMap::new(),
             in_use: BTreeSet::new()
         }

src/prolog/heap_print.rs

@@ -384,12 +384,12 @@ fn non_quoted_token<Iter: Iterator<Item=char>>(mut iter: Iter) -> bool {
             iter.next().is_none()
         } else if cut_char!(c) {
             iter.next().is_none()
-        } else if solo_char!(c) {
-            !iter.next().is_none()
         } else if c == '[' {
             (iter.next() == Some(']') && iter.next().is_none())
         } else if c == '{' {
             (iter.next() == Some('}') && iter.next().is_none())
+        } else if solo_char!(c) {
+            false // !iter.next().is_none()                
         } else {
             false
         }

src/prolog/lib/builtins.pl

@@ -249,10 +249,9 @@ must_be_var_names_list_([]).
 must_be_var_names_list_([VarName | VarNames]) :-
     (  nonvar(VarName), VarName = (Atom = _) ->
        (  atom(Atom) -> must_be_var_names_list_(VarNames)
-       ;  var(Atom) -> throw(error(instantiation_error, write_term/2))
        ;  throw(error(domain_error(write_options, variable_names(VarName)), write_term/2))
        )
-    ;  throw(error(instantiation_error, write_term/2))
+    ;  throw(error(domain_error(write_options, variable_names(VarName)), write_term/2))
     ).
 
 write_term(_, Options) :-

src/prolog/machine/machine_indices.rs

@@ -1,3 +1,5 @@
+use indexmap::IndexMap;
+
 use prolog_parser::ast::*;
 use prolog_parser::tabled_rc::*;
 
@@ -412,8 +414,8 @@ impl AddAssign<usize> for CodePtr {
     }
 }
 
-pub type HeapVarDict  = HashMap<Rc<Var>, Addr>;
-pub type AllocVarDict = HashMap<Rc<Var>, VarData>;
+pub type HeapVarDict  = IndexMap<Rc<Var>, Addr>;
+pub type AllocVarDict = IndexMap<Rc<Var>, VarData>;
 
 #[derive(Clone)]
 pub struct DynamicPredicateInfo {

src/prolog/machine/system_calls.rs

@@ -1558,7 +1558,7 @@ impl MachineState {
 
                         let mut list_of_var_eqs = vec![];
 
-                        for (var, binding) in term_write_result.var_dict {
+                        for (var, binding) in term_write_result.var_dict.into_iter().rev() {
                             let var_atom = clause_name!(var.to_string(), indices.atom_tbl);
                             let var_atom = Constant::Atom(var_atom, None);