Merge pull request #360 from notoria/master

Add get_single_char predicate.

README.md

@@ -168,8 +168,8 @@ predicates it defines. For example, with the program shown above:
 ;  What = pure_world.
 ```
 
-Press `SPACE` to show further answers, if any exist. Press `.` to
+Press `SPACE` to show further answers, if any exist. Press `RETURN` or
-abort the search and return to the toplevel prompt.
+ `.` to abort the search and return to the toplevel prompt.
 Press `h` to show a help message.
 
 To quit Scryer Prolog, use the standard predicate `halt/0`:

src/prolog/clause_types.rs

@@ -178,6 +178,7 @@ pub enum SystemClauseType {
     FetchGlobalVar,
     FetchGlobalVarWithOffset,
     GetChar,
+    GetSingleChar,
     ResetAttrVarState,
     TruncateIfNoLiftedHeapGrowthDiff,
     TruncateIfNoLiftedHeapGrowth,
@@ -241,7 +242,6 @@ pub enum SystemClauseType {
     InstallNewBlock,
     Maybe,
     QuotedToken,
-    RawInputReadChar,
     ReadTermFromChars,
     ResetBlock,
     ReturnFromVerifyAttr,
@@ -309,6 +309,7 @@ impl SystemClauseType {
                 clause_name!("$fetch_global_var_with_offset")
             }
             &SystemClauseType::GetChar => clause_name!("$get_char"),
+            &SystemClauseType::GetSingleChar => clause_name!("$get_single_char"),
             &SystemClauseType::ResetAttrVarState => clause_name!("$reset_attr_var_state"),
             &SystemClauseType::TruncateIfNoLiftedHeapGrowth => {
                 clause_name!("$truncate_if_no_lh_growth")
@@ -364,7 +365,6 @@ impl SystemClauseType {
             &SystemClauseType::QuotedToken => {
                 clause_name!("$quoted_token")
             }
-            &SystemClauseType::RawInputReadChar => clause_name!("$raw_input_read_char"),
             &SystemClauseType::RedoAttrVarBinding => clause_name!("$redo_attr_var_binding"),
             &SystemClauseType::RemoveCallPolicyCheck => clause_name!("$remove_call_policy_check"),
             &SystemClauseType::RemoveInferenceCounter => clause_name!("$remove_inference_counter"),
@@ -455,6 +455,7 @@ impl SystemClauseType {
             ("$fetch_global_var", 2) => Some(SystemClauseType::FetchGlobalVar),
             ("$fetch_global_var_with_offset", 3) => Some(SystemClauseType::FetchGlobalVarWithOffset),
             ("$get_char", 1) => Some(SystemClauseType::GetChar),
+            ("$get_single_char", 1) => Some(SystemClauseType::GetSingleChar),
             ("$points_to_cont_reset_marker", 1) => {
                 Some(SystemClauseType::PointsToContinuationResetMarker)
             }
@@ -506,7 +507,6 @@ impl SystemClauseType {
             ("$get_cp", 1) => Some(SystemClauseType::GetCutPoint),
             ("$install_new_block", 1) => Some(SystemClauseType::InstallNewBlock),
             ("$quoted_token", 1) => Some(SystemClauseType::QuotedToken),
-            ("$raw_input_read_char", 1) => Some(SystemClauseType::RawInputReadChar),
             ("$nextEP", 3) => Some(SystemClauseType::NextEP),
             ("$read_query_term", 2) => Some(SystemClauseType::ReadQueryTerm),
             ("$read_term", 2) => Some(SystemClauseType::ReadTerm),

src/prolog/lib/charsio.pl

@@ -1,4 +1,5 @@
-:- module(charsio, [read_term_from_chars/2,
+:- module(charsio, [get_single_char/1,
+                    read_term_from_chars/2,
                     write_term_to_chars/3]).
 
 :- use_module(library(iso_ext)).
@@ -56,6 +57,13 @@ extend_var_list_([V|Vs], N, VarList, NewVarList, VarType) :-
     ).
 
 
+get_single_char(C) :-
+    (  var(C) -> '$get_single_char'(C)
+    ;  atom_length(C, 1) -> '$get_single_char'(C)
+    ;  throw(error(domain_error(in_character, C), get_single_char/1))
+    ).
+
+
 read_term_from_chars(Chars, Term) :-
     (  var(Chars) ->
        throw(error(instantiation_error, read_term_from_chars/2))

src/prolog/machine/system_calls.rs

@@ -31,40 +31,30 @@ use std::rc::Rc;
 use crate::crossterm::event::{read, Event, KeyCode, KeyEvent};
 use crate::crossterm::terminal::{enable_raw_mode, disable_raw_mode};
 
-pub enum ContinueResult {
+pub fn get_single_char() -> char {
-    ContinueQuery,
+    let c;
-    Conclude,
+    enable_raw_mode().expect("failed to enable raw mode");
-    Help,
-    PrintWithoutMaxDepth,
-    PrintWithMaxDepth
-}
-
-pub fn next_keypress() -> ContinueResult {
     loop {
-        match read() {
+        if let Ok(Event::Key(KeyEvent { code, .. })) = read() {
-            Ok(Event::Key(KeyEvent { code, .. })) => {
             match code {
-                    KeyCode::Char('w') => {
+                KeyCode::Char(ch) => {
-                        return ContinueResult::PrintWithoutMaxDepth;
+                    c = ch;
-                    }
+                    break;
-                    KeyCode::Char('p') => {
+                },
-                        return ContinueResult::PrintWithMaxDepth;
+                KeyCode::Enter => {
-                    }
+                    c = '\n';
-                    KeyCode::Char(' ') | KeyCode::Char(';') | KeyCode::Char('n') => {
+                    break;
-                        return ContinueResult::ContinueQuery;
+                },
-                    }
+                KeyCode::Tab => {
-                    KeyCode::Char('.') => {
+                    c = '\t';
-                        return ContinueResult::Conclude;
+                    break;
-                    }
+                },
-                    KeyCode::Char('h') => {
+                _ => ()
-                        return ContinueResult::Help;
-                    }
-                    _ => {}
             }
         }
-            _ => {}
-        }
     }
+    disable_raw_mode().expect("failed to disable raw mode");
+    c
 }
 
 struct BrentAlgState {
@@ -1463,6 +1453,13 @@ impl MachineState {
                     }
                 }
             }
+            &SystemClauseType::GetSingleChar => {
+                let c = get_single_char();
+
+                let a1 = self[temp_v!(1)];
+
+                self.unify(Addr::Char(c), a1);
+            }
             &SystemClauseType::GetModuleClause => {
                 let module = self[temp_v!(3)];
                 let head = self[temp_v!(1)];
@@ -2880,26 +2877,6 @@ impl MachineState {
             &SystemClauseType::InstallNewBlock => {
                 self.install_new_block(temp_v!(1));
             }
-            &SystemClauseType::RawInputReadChar => {
-		let keypress = {
-                    enable_raw_mode().expect("failed to transition into raw mode");
-		    let result = next_keypress();
-                    disable_raw_mode().expect("failed to transition out of raw mode");
-
-                    result
-		};
-
-                let c = match keypress {
-                    ContinueResult::ContinueQuery => ';',
-                    ContinueResult::Conclude => '.',
-                    ContinueResult::Help => 'h',
-                    ContinueResult::PrintWithoutMaxDepth => 'w',
-                    ContinueResult::PrintWithMaxDepth => 'p',
-                };
-
-                let target = self[temp_v!(1)];
-                self.unify(Addr::Char(c), target);
-            }
             &SystemClauseType::NextEP => {
                 let first_arg = self.store(self.deref(self[temp_v!(1)]));
 

src/prolog/toplevel.pl

@@ -145,30 +145,31 @@
     ).
 
 '$read_input'(ThreadedGoals, NewVarList) :-
-    '$raw_input_read_char'(C),
+    get_single_char(C),
-    (  C == w ->
+    (  C = w ->
        nl,
        write('   '),
        '$write_eq'(ThreadedGoals, NewVarList, 0),
        '$read_input'(ThreadedGoals, NewVarList)
-    ;  C == p ->
+    ;  C = p ->
        nl,
        write('   '),
        '$write_eq'(ThreadedGoals, NewVarList, 20),
        '$read_input'(ThreadedGoals, NewVarList)
-    ;  C == (';') ->
+    ;  member(C, [';', ' ', n]) ->
        nl, write(';  '), false
-    ;  C == h ->
+    ;  C = h ->
        '$help_message',
        '$read_input'(ThreadedGoals, NewVarList)
-    ;  C == '.',
+    ;  member(C, ['\n', .]) ->
        nl, write(';  ...'), nl
+    ; '$read_input'(ThreadedGoals, NewVarList)
     ).
 
 '$help_message' :-
     nl, nl,
     write('SPACE, "n" or ";": next solution, if any\n'),
-    write('".": stop enumeration\n'),
+    write('RETURN or ".": stop enumeration\n'),
     write('"h": display this help message\n'),
     write('"w": write terms without depth limit\n'),
     write('"p": print terms with depth limit\n\n').