Tweaked cov.py, summary.py, to render fraction percents as notes

This matches how diff percentages are rendered, and simplifies the
internal table rendering by making Frac less of a special case. It also
allows for other type notes in the future.

One concern is how all the notes are shoved to the side, which may make
it a bit harder to find related percentages. If this becomes annoying we
should probably look into interspersing all notes (including diff
percentages) between the relevant columns.

Before:

  function                                   lines            branches
  lfsr_rbyd_appendattr             230/231   99.6%     172/192   89.6%
  lfsr_rbyd_p_recolor                33/34   97.1%       11/12   91.7%
  lfs_alloc                          40/42   95.2%       21/24   87.5%
  lfsr_rbyd_appendcompaction         54/57   94.7%       39/42   92.9%
  ...

After:

  function                           lines    branches
  lfsr_rbyd_appendattr             230/231     172/192 (99.6%, 89.6%)
  lfsr_rbyd_p_recolor                33/34       11/12 (97.1%, 91.7%)
  lfs_alloc                          40/42       21/24 (95.2%, 87.5%)
  lfsr_rbyd_appendcompaction         54/57       39/42 (94.7%, 92.9%)
  ...

scripts/structs.py

@@ -63,10 +63,7 @@ class Int(co.namedtuple('Int', 'x')):
     def table(self):
         return '%7s' % (self,)
 
-    diff_none = '%7s' % '-'
-    diff_table = table
-
-    def diff_diff(self, other):
+    def diff(self, other):
         new = self.x if self else 0
         old = other.x if other else 0
         diff = new - old
@@ -375,7 +372,7 @@ def table(Result, results, diff_results=None, *,
     header.append('')
     lines.append(header)
 
-    def table_entry(name, r, diff_r=None, ratios=[]):
+    def table_entry(name, r, diff_r=None):
         entry = []
         entry.append(name)
         if diff_results is None:
@@ -385,37 +382,43 @@ def table(Result, results, diff_results=None, *,
                     else types[k].none)
         elif percent:
             for k in fields:
-                entry.append(getattr(r, k).diff_table()
+                entry.append(getattr(r, k).table()
                     if getattr(r, k, None) is not None
-                    else types[k].diff_none)
+                    else types[k].none)
         else:
             for k in fields:
-                entry.append(getattr(diff_r, k).diff_table()
+                entry.append(getattr(diff_r, k).table()
                     if getattr(diff_r, k, None) is not None
-                    else types[k].diff_none)
+                    else types[k].none)
             for k in fields:
-                entry.append(getattr(r, k).diff_table()
+                entry.append(getattr(r, k).table()
                     if getattr(r, k, None) is not None
-                    else types[k].diff_none)
+                    else types[k].none)
             for k in fields:
-                entry.append(types[k].diff_diff(
+                entry.append(types[k].diff(
                         getattr(r, k, None),
                         getattr(diff_r, k, None)))
         if diff_results is None:
-            entry.append('')
-        elif percent:
-            entry.append(' (%s)' % ', '.join(
-                '+∞%' if t == +m.inf
-                else '-∞%' if t == -m.inf
-                else '%+.1f%%' % (100*t)
-                for t in ratios))
+            notes = []
+            for k in fields:
+                try:
+                    notes.extend(getattr(r, k).notes())
+                except AttributeError:
+                    pass
+            entry.append(' (%s)' % ', '.join(notes)
+                if notes else '')
         else:
+            ratios = [
+                types[k].ratio(
+                    getattr(r, k, None),
+                    getattr(diff_r, k, None))
+                for k in fields]
             entry.append(' (%s)' % ', '.join(
                     '+∞%' if t == +m.inf
                     else '-∞%' if t == -m.inf
                     else '%+.1f%%' % (100*t)
                     for t in ratios)
-                if any(ratios) else '')
+                if percent or any(ratios) else '')
         return entry
 
     # entries
@@ -424,34 +427,26 @@ def table(Result, results, diff_results=None, *,
             r = table.get(name)
             if diff_results is None:
                 diff_r = None
-                ratios = None
             else:
                 diff_r = diff_table.get(name)
-                ratios = [
-                    types[k].ratio(
-                        getattr(r, k, None),
-                        getattr(diff_r, k, None))
-                    for k in fields]
-                if not all_ and not any(ratios):
+                if not all_ and not any(
+                        types[k].ratio(
+                            getattr(r, k, None),
+                            getattr(diff_r, k, None))
+                        for k in fields):
                     continue
-            lines.append(table_entry(name, r, diff_r, ratios))
+            lines.append(table_entry(name, r, diff_r))
 
     # total
     r = next(iter(fold(Result, results, by=[])), None)
     if diff_results is None:
         diff_r = None
-        ratios = None
     else:
         diff_r = next(iter(fold(Result, diff_results, by=[])), None)
-        ratios = [
-            types[k].ratio(
-                getattr(r, k, None),
-                getattr(diff_r, k, None))
-            for k in fields]
-    lines.append(table_entry('TOTAL', r, diff_r, ratios))
+    lines.append(table_entry('TOTAL', r, diff_r))
 
-    # find the best widths, note that column 0 contains the names and column -1
-    # the ratios, so those are handled a bit differently
+    # find the best widths, note that column 0 contains the names and
+    # column -1 the ratios/notes, so those are handled a bit differently
     widths = [
         ((max(it.chain([w], (len(l[i]) for l in lines)))+1+4-1)//4)*4-1
         for w, i in zip(