Added lambda expression (user/automatically defined functions

eo/contrib/mathsym/test/test_lambda.cpp

@@ -0,0 +1,34 @@
+#include <FunDef.h>
+
+using namespace std;
+
+int main() {
+
+    Sym x = SymVar(0);
+    Sym y = SymVar(1);
+
+    Sym f = y + x*x;
+
+    Sym l = SymLambda(f);
+    
+    SymVec args = l.args();
+    args[0] = x;
+    args[1] = y;
+    l = Sym(l.token(), args);
+    
+    vector<double> v(3);
+    v[0] = 2.0;
+    v[1] = 3.0;
+    v[2] = 4.0;
+
+    double v1 = eval(f,v);
+    double v2 = eval(l,v);
+
+    cout << v1 << ' ' << v2 << endl;
+    cout << f << endl;
+    cout << l << endl;
+
+    if (v1 != 7.0) return 1;
+    if (v2 != 11.0) return 1;
+}
+