X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=ginac%2Foperators.cpp;h=6cf750cefa7005542175ee6d46f2178a18a34787;hp=9a681b5ea2e2e68f263e40caad0c3956af4cc476;hb=956a3ad3779759028bfd742456ed9eafc3e85063;hpb=79eebbd4ebb7b5f7c6517298c728a16a68282ace

diff --git a/ginac/operators.cpp b/ginac/operators.cpp
index 9a681b5e..6cf750ce 100644
--- a/ginac/operators.cpp
+++ b/ginac/operators.cpp
@@ -29,6 +29,7 @@
 #include "numeric.h"
 #include "power.h"
 #include "relational.h"
+#include "input_lexer.h"
 #include "debugmsg.h"
 #include "utils.h"
 
@@ -335,9 +336,21 @@ ostream & operator<<(ostream & os, const ex & e)
     return os;
 }
 
+/** Input (parse) expression from stream. The input grammar is similar to the
+ *  GiNaC output format. If 'e' contains a list of symbols upon entry, these
+ *  symbols are used in the parsed expression in all places where symbols with
+ *  the same names appear. All other encountered symbols will be newly created. */
 istream & operator>>(istream & is, ex & e)
 {
-    throw(std::logic_error("input from streams not yet implemented"));
+	string s;
+	getline(is, s);
+	set_lexer_string(s);
+	set_lexer_symbols(e);
+	ginac_yyrestart(NULL);
+	if (yyparse())
+		throw (std::runtime_error(get_parser_error()));
+	else
+		e = parsed_ex;
 }
 
 #ifndef NO_NAMESPACE_GINAC