parser: map input strings onto arbitrary expressions (not only symbols).

[ginac.git] / ginac / parser / parse_context.cpp

diff --git a/ginac/parser/parse_context.cpp b/ginac/parser/parse_context.cpp
index e4956ba74d4510d234beeee023722b2c7240a2f9..1dd767778f9581cea6ad0b6e8790d400b38733c8 100644 (file)
--- a/ginac/parser/parse_context.cpp
+++ b/ginac/parser/parse_context.cpp
@@ -4,23 +4,28 @@
 namespace GiNaC
 {
 
-const symbol&
+symbol
 find_or_insert_symbol(const std::string& name, symtab& syms, const bool strict)
 {
        symtab::const_iterator p = syms.find(name);
-       if (p != syms.end())
-               return p->second.first;
+       if (p != syms.end()) {
+               if (is_a<symbol>(p->second))
+                       return ex_to<symbol>(p->second);
+               else
+                       throw std::invalid_argument(
+                               std::string("find_or_insert_symbol: name \"")
+                               + name + "\" does not correspond to a symbol");
+       }
+
 
        if (strict)
                throw std::invalid_argument(
                                std::string("find_or_insert_symbol: symbol \"") 
                                + name + "\" not found");
 
-       // false means this symbol was created by parser 
-       const std::pair<symbol, bool> tmp = std::make_pair(symbol(name), false);
-
-       symtab::iterator i = syms.insert(symtab::value_type(name, tmp)).first;
-       return i->second.first;
+       const symbol sy(name);
+       syms[name] = sy;
+       return sy;
 }
 
 }