From 7ff11dce35e16e732db3ebb8758be19e941b89dc Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Sun, 15 Mar 2020 13:16:40 +0100
Subject: [PATCH 1/2] support 'p' to reprint answer with max depth, allowing w
 -> p -> w ...

---
 src/prolog/machine/system_calls.rs |  5 +++++
 src/prolog/toplevel.pl             | 11 ++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/prolog/machine/system_calls.rs b/src/prolog/machine/system_calls.rs
index 2b521d40..9e426227 100644
--- a/src/prolog/machine/system_calls.rs
+++ b/src/prolog/machine/system_calls.rs
@@ -34,6 +34,7 @@ pub enum ContinueResult {
     ContinueQuery,
     Conclude,
     PrintWithoutMaxDepth,
+    PrintWithMaxDepth
 }
 
 pub fn next_keypress() -> ContinueResult {
@@ -44,6 +45,9 @@ pub fn next_keypress() -> ContinueResult {
                     KeyCode::Char('w') => {
                         return ContinueResult::PrintWithoutMaxDepth;
                     }
+                    KeyCode::Char('p') => {
+                        return ContinueResult::PrintWithMaxDepth;
+                    }
                     KeyCode::Char(' ') | KeyCode::Char(';') | KeyCode::Char('n') => {
                         return ContinueResult::ContinueQuery;
                     }
@@ -2348,6 +2352,7 @@ impl MachineState {
                     ContinueResult::ContinueQuery => ';',
                     ContinueResult::Conclude => '.',
                     ContinueResult::PrintWithoutMaxDepth => 'w',
+                    ContinueResult::PrintWithMaxDepth => 'p',
                 };
 
                 let target = self[temp_v!(1)].clone();
diff --git a/src/prolog/toplevel.pl b/src/prolog/toplevel.pl
index edf00883..be7b255a 100644
--- a/src/prolog/toplevel.pl
+++ b/src/prolog/toplevel.pl
@@ -184,14 +184,19 @@
 
 '$read_input'(ThreadedGoals, NewVarList) :-
     '$raw_input_read_char'(C),
-    (  C == ('w'), !,
+    (  C == w ->
        nl,
        write('   '),
        '$write_eq'(ThreadedGoals, NewVarList, 0),
        '$read_input'(ThreadedGoals, NewVarList)
-    ;  C == (';'), !,
+    ;  C == p ->
+       nl,
+       write('   '),
+       '$write_eq'(ThreadedGoals, NewVarList, 20),
+       '$read_input'(ThreadedGoals, NewVarList)
+    ;  C == (';') ->
        nl, write(';  '), false
-    ;  C == ('.'), !,
+    ;  C == '.',
        nl, write('   ...'), nl
     ).
 

From 17a448e0452cbd4121903fdb9f75b67b320daf86 Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Sun, 15 Mar 2020 13:24:28 +0100
Subject: [PATCH 2/2] support 'h' to print help message during toplevel
 interaction

---
 src/prolog/machine/system_calls.rs |  5 +++++
 src/prolog/toplevel.pl             | 11 +++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/prolog/machine/system_calls.rs b/src/prolog/machine/system_calls.rs
index 9e426227..03ec8311 100644
--- a/src/prolog/machine/system_calls.rs
+++ b/src/prolog/machine/system_calls.rs
@@ -33,6 +33,7 @@ use crate::crossterm::terminal::{enable_raw_mode, disable_raw_mode};
 pub enum ContinueResult {
     ContinueQuery,
     Conclude,
+    Help,
     PrintWithoutMaxDepth,
     PrintWithMaxDepth
 }
@@ -54,6 +55,9 @@ pub fn next_keypress() -> ContinueResult {
                     KeyCode::Char('.') => {
                         return ContinueResult::Conclude;
                     }
+                    KeyCode::Char('h') => {
+                        return ContinueResult::Help;
+                    }
                     _ => {}
                 }
             }
@@ -2351,6 +2355,7 @@ impl MachineState {
                 let c = match keypress {
                     ContinueResult::ContinueQuery => ';',
                     ContinueResult::Conclude => '.',
+                    ContinueResult::Help => 'h',
                     ContinueResult::PrintWithoutMaxDepth => 'w',
                     ContinueResult::PrintWithMaxDepth => 'p',
                 };
diff --git a/src/prolog/toplevel.pl b/src/prolog/toplevel.pl
index be7b255a..3abadd7c 100644
--- a/src/prolog/toplevel.pl
+++ b/src/prolog/toplevel.pl
@@ -196,10 +196,21 @@
        '$read_input'(ThreadedGoals, NewVarList)
     ;  C == (';') ->
        nl, write(';  '), false
+    ;  C == h ->
+       '$help_message',
+       '$read_input'(ThreadedGoals, NewVarList)
     ;  C == '.',
        nl, write('   ...'), nl
     ).
 
+'$help_message' :-
+    nl, nl,
+    write('SPACE, "n" or ";": next solution, if any\n'),
+    write('".": stop enumeration\n'),
+    write('"h": display this help message\n'),
+    write('"w": write terms without depth limit\n'),
+    write('"p": print terms with depth limit\n\n').
+
 '$gather_query_vars'([_ = Var | Vars], QueryVars) :-
     (  var(Var) ->
        QueryVars = [Var | QueryVars1],