Faster, better (recursive descent) expression parser.

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

diff --git a/ginac/parser/parse_context.cpp b/ginac/parser/parse_context.cpp
new file mode 100644 (file)
index 0000000..e4956ba
--- /dev/null
+++ b/ginac/parser/parse_context.cpp
@@ -0,0 +1,27 @@
+#include "parse_context.hpp"
+#include <sstream>
+#include <stdexcept>
+namespace GiNaC
+{
+
+const 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 (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;
+}
+
+}
+