respect ambiguity with ., add ... to indicate more answers

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "scryer-prolog"
-version = "0.8.75"
+version = "0.8.76"
 authors = ["Mark Thom <markjordanthom@gmail.com>"]
 repository = "https://github.com/mthom/scryer-prolog"
 description = "A modern Prolog implementation written mostly in Rust."

src/prolog/heap_print.rs

@@ -195,11 +195,11 @@ impl HCValueOutputter for PrinterOutputter {
         PrinterOutputter { contents: String::new() }
     }
 
-    fn append(&mut self, contents: &str) {        
+    fn append(&mut self, contents: &str) {
         if requires_space(&self.contents, contents) {
             self.push_char(' ');
         }
-        
+
         self.contents += contents;
     }
 
@@ -320,7 +320,7 @@ pub fn requires_space(atom: &str, op: &str) -> bool {
     match atom.chars().last() {
         Some(ac) => op.chars().next().map(|oc| {
             if ac == '0' {
-                oc == 'b' || oc == 'x' || oc == 'o' || !non_quoted_token(op.chars())
+                oc == 'b' || oc == 'x' || oc == 'o' || oc == '\''
             } else if alpha_numeric_char!(ac) {
                 oc == '(' || alpha_numeric_char!(oc)
             } else if graphic_token_char!(ac) {
@@ -575,7 +575,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter>
     #[inline]
     fn append_str(&mut self, s: &str) {
         self.last_item_idx = self.outputter.len();
-        self.outputter.append(s);            
+        self.outputter.append(s);
     }
 
     fn offset_as_string(&self, addr: Addr) -> Option<String> {
@@ -795,7 +795,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter>
                     }
                 } else if !self.at_cdr("") {
                     self.append_str("[]");
-                },            
+                },
             DoubleQuotes::Atom => {
                 let borrowed_str = s.borrow();
 
@@ -805,7 +805,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter>
             }
         }
     }
-    
+
     fn push_list(&mut self) {
         let cell = Rc::new(Cell::new(true));
 

src/prolog/machine/machine_state_impl.rs

@@ -1828,7 +1828,7 @@ impl MachineState {
                             } else {
                                 self.fail = true;
                             }
-                        },
+                        }
                     _ => // 8.5.2.3 d)
                         return Err(self.error_form(MachineError::type_error(ValidType::Compound, term),
                                                    stub))

src/prolog/machine/mod.rs

@@ -465,8 +465,10 @@ impl Machine {
 
                     if !(self.machine_st.b > 0) {
                         if bindings.is_empty() {
+                            let space = if requires_space(&attr_goals, ".") { " " } else { "" };
+                            
                             if !attr_goals.is_empty() {
-                                println!("{}.", attr_goals);
+                                println!("{}{}.", attr_goals, space);
                             } else {
                                 println!("true.");
                             }
@@ -483,24 +485,24 @@ impl Machine {
 
                     if !attr_goals.is_empty() {
                         if bindings.is_empty() {
-                            let space = if requires_space(&attr_goals, ".") { " " } else { "" };
+                            write!(raw_stdout, "{}", attr_goals).unwrap();
-                            write!(raw_stdout, "{}{}", attr_goals, space).unwrap();
                         } else {
-                            let space = if requires_space(&attr_goals, ".") { " " } else { "" };
+                            write!(raw_stdout, "{}, {}", bindings, attr_goals).unwrap();
-                            write!(raw_stdout, "{}, {}{}", bindings, attr_goals, space).unwrap();
                         }
                     } else if !bindings.is_empty() {
-                        let space = if requires_space(&bindings, ".") { " " } else { "" };
+                        write!(raw_stdout, "{}", bindings).unwrap();
-                        write!(raw_stdout, "{}{}", bindings, space).unwrap();
                     }
 
                     if self.machine_st.b > 0 {
                         raw_stdout.flush().unwrap();
 
-                        let result = match next_keypress(raw_stdout) {
+                        let result = match next_keypress() {
-                            ContinueResult::ContinueQuery =>
+                            ContinueResult::ContinueQuery => {
-                                self.continue_query(&alloc_locs, &mut heap_locs),
+                                write!(raw_stdout, " ;\r\n").unwrap();
+                                self.continue_query(&alloc_locs, &mut heap_locs)
+                            },
                             ContinueResult::Conclude => {
+                                write!(raw_stdout, " ...\r\n").unwrap();
                                 self.machine_st.absorb_snapshot(snapshot);
                                 return;
                             }
@@ -531,7 +533,13 @@ impl Machine {
                         if bindings.is_empty() && attr_goals.is_empty() {
                             write!(raw_stdout, "true.\r\n").unwrap();
                         } else {
-                            write!(raw_stdout, ".\r\n").unwrap();
+                            let space = if !attr_goals.is_empty() {
+                                if requires_space(&attr_goals, ".") { " " } else { "" }
+                            } else {
+                                if requires_space(&bindings, ".") { " " } else { "" }
+                            };
+                            
+                            write!(raw_stdout, "{}.\r\n", space).unwrap();
                         }
 
                         break;

src/prolog/toplevel.pl

@@ -15,6 +15,6 @@ read_and_match :-
     !.
 
 '$print_exception'(E) :-
-    write_term('error: exception thrown: ', [quoted(false)]),
+    write_term('caught: ', [quoted(false)]),
     writeq(E),
     nl.

src/prolog/write.rs

@@ -6,9 +6,8 @@ use prolog::machine::machine_indices::*;
 
 use termion::input::TermRead;
 use termion::event::Key;
-use termion::raw::{RawTerminal};
 
-use std::io::{Write, stdin};
+use std::io::stdin;
 use std::fmt;
 
 impl fmt::Display for LocalCodePtr {
@@ -364,20 +363,16 @@ pub enum ContinueResult {
 }
 
 pub
-fn next_keypress(mut stdout: RawTerminal<std::io::Stdout>) -> ContinueResult
+fn next_keypress() -> ContinueResult
 {
     let stdin = stdin();
 
     for c in stdin.keys() {
         match c.unwrap() {
-            Key::Char(' ') | Key::Char(';') => {
+            Key::Char(' ') | Key::Char(';') =>
-                write!(stdout, " ;\r\n").unwrap();
+                return ContinueResult::ContinueQuery,
-                return ContinueResult::ContinueQuery;
+            Key::Char('.') =>
-            },
+                return ContinueResult::Conclude,
-            Key::Char('.') => {
-                write!(stdout, " .\r\n").unwrap();
-                return ContinueResult::Conclude;
-            },
             _ => {}
         }
     }