Minor simplifications to valexpr parser

The most significant change is the way CONS sequences are parsed, and
that now instead of =/:=, the operators are ==/=.

1 files changed, 21 insertions, 5 deletions

diff --git a/src/expr.cc b/src/expr.cc
index bcf83edb..b3d4abcd 100644
--- a/src/expr.cc
+++ b/src/expr.cc
@@ -167,22 +167,38 @@ value_t source_command(call_scope_t& args)
 {
   std::istream * in = NULL;
   scoped_ptr<ifstream> stream;
+  string pathname;
 
   if (args.has(0)) {
-    stream.reset(new ifstream(path(args.get<string>(0))));
+    pathname = args.get<string>(0);
+    stream.reset(new ifstream(path(pathname)));
     in = stream.get();
   } else {
+    pathname = "<stdin>";
     in = &std::cin;
   }
 
-  symbol_scope_t file_locals(args);
+  symbol_scope_t   file_locals(args);
+  std::size_t      linenum = 0;
+  char             buf[4096];
+  istream_pos_type pos;
 
   while (in->good() && ! in->eof()) {
-    char buf[4096];
+    pos = in->tellg();
     in->getline(buf, 4095);
+    linenum++;
 
-    if (buf[0] != ';')
-      expr_t(buf).calc(file_locals);
+    char * p = skip_ws(buf);
+    if (*p && *p != ';') {
+      try {
+        expr_t(p).calc(file_locals);
+      }
+      catch (const std::exception&) {
+        add_error_context(_("While parsing value expression on line %1:")
+                          << linenum);
+        add_error_context(source_context(pathname, pos, in->tellg(), "> "));
+      }
+    }
   }
 
   return true;