From 997f9af4fa07e9679d4bea962a21673be79c6701 Mon Sep 17 00:00:00 2001
From: Tim Vieira <tim.f.vieira@gmail.com>
Date: Tue, 2 Jul 2013 00:14:51 -0400
Subject: [PATCH] tweaks to trace to print lists nicely, and infix 'in'

Simplify error message pertaining to retracting a rule and when a query or trace
fails.
---
 src/Dyna/Backend/Python/post/trace.py | 29 +++++++++++++++++++++++----
 src/Dyna/Backend/Python/repl.py       | 13 +++++++++---
 src/Dyna/Backend/Python/stdlib.py     |  9 +++++++--
 3 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/src/Dyna/Backend/Python/post/trace.py b/src/Dyna/Backend/Python/post/trace.py
index dbdb5bc..a01d601 100644
--- a/src/Dyna/Backend/Python/post/trace.py
+++ b/src/Dyna/Backend/Python/post/trace.py
@@ -56,12 +56,14 @@ def dig(head, visited, tail, groups, interp):
     if head in tail:
         return ['%s = %s' % (yellow % head, head.value)] \
             + ['|'] \
-            + branch([[red % 'continue as before (cyclic structure, will continue forever)']])
+            + branch([[red % 'continue as before (cyclic structure, will continue forever)']]) \
+            + ['']
 
     if head in visited:
         return ['%s = %s' % (yellow % head, head.value)] \
             + ['|'] \
-            + branch([[red % 'continue as before (shared structure)']])
+            + branch([[red % 'continue as before (shared structure)']]) \
+            + ['']
 
     if head not in groups:
         return []
@@ -83,7 +85,8 @@ def dig(head, visited, tail, groups, interp):
 
     return ['%s = %s' % (yellow % head, cyan % _repr(head.value))] \
         + ['|'] \
-        + branch(contribs) + ['']
+        + branch(contribs) #\
+#        + ['']
 
 
 def branch(xs):
@@ -171,12 +174,16 @@ class Crux(object):
                 return label
 
             fn_args = [self.get_function(y) for y in x.body]
-            if not label.isalpha() and not label.startswith('&') and len(fn_args) == 2:  # infix
+
+            # infix
+            if (not label.isalpha() and not label.startswith('&') and len(fn_args) == 2) \
+                    or label in ('in', 'and', 'or'):
                 [a,b] = fn_args
                 return '(%s %s %s)' % (a, label, b)
             return '%s(%s)' % (label, ', '.join(fn_args))
 
         else:
+
             if not g.incoming[x]:  # input
                 if re.match('u[A-Z].*', x):                          # user variable
                     return x[1:] + (cyan % '=%s' % self.values(x))
@@ -184,11 +191,25 @@ class Crux(object):
 
             if len(g.incoming[x]) > 1:
                 return ' = '.join('(%s%s)' % (self.get_function(e), (cyan % '=%s' % self.values(e.head))) for e in g.incoming[x])
+
             [e] = g.incoming[x]
 
             if e.label == '=':
                 return self.get_function(e)
 
+            # handle lists
+            if e.label == '& cons':
+                _e = e
+                a = []
+                while e.label == '& cons':
+                    x, xs = e.body
+                    [e] = g.incoming[xs]
+                    a.append(self.get_function(x))
+                if e.label == '& nil':
+                    return '[%s]' % ', '.join(a)
+                else:
+                    return self.get_function(_e)          # malformed list.
+
             if e.label.startswith('&'):
                 return self.get_function(e)
 
diff --git a/src/Dyna/Backend/Python/repl.py b/src/Dyna/Backend/Python/repl.py
index d88525f..e0dfc04 100644
--- a/src/Dyna/Backend/Python/repl.py
+++ b/src/Dyna/Backend/Python/repl.py
@@ -171,18 +171,22 @@ class REPL(cmd.Cmd, object):
 
         try:
             query = "$query dict= %s." % q
+
             self.default(query, show_changed=False)
+
             try:
                 [(_, _, results)] = self.interp.chart['$query/0'][:,]
                 return results
             except ValueError:
                 return []
+
         finally:
 
             # cleanup:
             # retract newly added rules.
             for r in self.interp.new_rules:
-                self.interp.retract_rule(r)
+                if r in self.interp.rules:
+                    self.interp.retract_rule(r)
 
             try:
                 # drop $out chart
@@ -203,7 +207,7 @@ class REPL(cmd.Cmd, object):
         if len(results) == 0:
             print 'No results.'
             return
-        for val, bindings in results:
+        for val, bindings in sorted(results):
             print _repr(val), 'where', drepr(dict(bindings))
         print
 
@@ -541,7 +545,9 @@ class REPL(cmd.Cmd, object):
 
         try:
             query = "$trace dict= _ is %s, &(%s)." % (q,q)
+
             self.default(query, show_changed=False)
+
             try:
                 [(_, _, results)] = self.interp.chart['$trace/0'][:,]
             except ValueError:
@@ -558,7 +564,8 @@ class REPL(cmd.Cmd, object):
             # cleanup:
             # retract newly added rules.
             for r in self.interp.new_rules:
-                self.interp.retract_rule(r)
+                if r in self.interp.rules:
+                    self.interp.retract_rule(r)
 
             try:
                 # drop $out chart
diff --git a/src/Dyna/Backend/Python/stdlib.py b/src/Dyna/Backend/Python/stdlib.py
index 7b1d8da..006c4bf 100644
--- a/src/Dyna/Backend/Python/stdlib.py
+++ b/src/Dyna/Backend/Python/stdlib.py
@@ -13,6 +13,11 @@ except ImportError:                       # XXX: should probably issue a warning
 def split(s, delim='\s+'):
     return todynalist(re.split(delim, s))
 
+def crash():
+    class Crasher(Exception):
+        pass
+    raise Crasher('Hey, you asked for it!')
+
 def pycall(name, *args):
     """
     Temporary foreign function interface - call Python functions from dyna!
@@ -22,12 +27,12 @@ def pycall(name, *args):
     return todyna(x)
 
 def todyna(x):
-    if isinstance(x, (list, tuple)):
+    if isinstance(x, (set, list, tuple)):
         return todynalist(x)
     return x
 
 def topython(x):
-    if isinstance(x, (Cons, Nil)):
+    if isinstance(x, Cons) or x is Nil:
         return x.aslist
     return x
 
-- 
2.50.1