- New code capability: a read-only string cache. Start of solution for

Savannah bug #15182, but not much uses it yet.  Coming shortly.
- Added short-circuiting $(and ..) and $(or ...) functions.

function.c

@@ -1230,6 +1230,110 @@ func_if (char *o, char **argv, const char *funcname UNUSED)
   return o;
 }
 
+/*
+  $(or condition1[,condition2[,condition3[...]]])
+
+  A CONDITION is false iff it evaluates to an empty string.  White
+  space before and after CONDITION are stripped before evaluation.
+
+  CONDITION1 is evaluated.  If it's true, then this is the result of
+  expansion.  If it's false, CONDITION2 is evaluated, and so on.  If none of
+  the conditions are true, the expansion is the empty string.
+
+  Once a CONDITION is true no further conditions are evaluated
+  (short-circuiting).
+*/
+
+static char *
+func_or (char *o, char **argv, const char *funcname UNUSED)
+{
+  for ( ; *argv ; ++argv)
+    {
+      const char *begp = *argv;
+      const char *endp = begp + strlen (*argv) - 1;
+      char *expansion;
+      int result = 0;
+
+      /* Find the result of the condition: if it's false keep going.  */
+
+      strip_whitespace (&begp, &endp);
+
+      if (begp > endp)
+        continue;
+
+      expansion = expand_argument (begp, endp+1);
+      result = strlen (expansion);
+
+      /* If the result is false keep going.  */
+      if (!result)
+        {
+          free (expansion);
+          continue;
+        }
+
+      /* It's true!  Keep this result and return.  */
+      o = variable_buffer_output (o, expansion, result);
+      free (expansion);
+      break;
+    }
+
+  return o;
+}
+
+/*
+  $(and condition1[,condition2[,condition3[...]]])
+
+  A CONDITION is false iff it evaluates to an empty string.  White
+  space before and after CONDITION are stripped before evaluation.
+
+  CONDITION1 is evaluated.  If it's false, then this is the result of
+  expansion.  If it's true, CONDITION2 is evaluated, and so on.  If all of
+  the conditions are true, the expansion is the result of the last condition.
+
+  Once a CONDITION is false no further conditions are evaluated
+  (short-circuiting).
+*/
+
+static char *
+func_and (char *o, char **argv, const char *funcname UNUSED)
+{
+  char *expansion;
+  int result;
+
+  while (1)
+    {
+      const char *begp = *argv;
+      const char *endp = begp + strlen (*argv) - 1;
+
+      /* An empty condition is always false.  */
+      strip_whitespace (&begp, &endp);
+      if (begp > endp)
+        return o;
+
+      expansion = expand_argument (begp, endp+1);
+      result = strlen (expansion);
+
+      /* If the result is false, stop here: we're done.  */
+      if (!result)
+        break;
+
+      /* Otherwise the result is true.  If this is the last one, keep this
+         result and quit.  Otherwise go on to the next one!  */
+
+      if (*(++argv))
+        free (expansion);
+      else
+        {
+          o = variable_buffer_output (o, expansion, result);
+          break;
+        }
+    }
+
+  free (expansion);
+
+  return o;
+}
+
 static char *
 func_wildcard (char *o, char **argv, const char *funcname UNUSED)
 {
@@ -1977,6 +2081,8 @@ static struct function_table_entry function_table_init[] =
   { STRING_SIZE_TUPLE("error"),         0,  1,  1,  func_error},
   { STRING_SIZE_TUPLE("warning"),       0,  1,  1,  func_error},
   { STRING_SIZE_TUPLE("if"),            2,  3,  0,  func_if},
+  { STRING_SIZE_TUPLE("or"),            1,  0,  0,  func_or},
+  { STRING_SIZE_TUPLE("and"),           1,  0,  0,  func_and},
   { STRING_SIZE_TUPLE("value"),         0,  1,  1,  func_value},
   { STRING_SIZE_TUPLE("eval"),          0,  1,  1,  func_eval},
 #ifdef EXPERIMENTAL