fix parsing of z value

The `substr` function was going a character too far making the `fail` function from istringstream
function failing.

`testKlass` is working again.

src/camel/Engine.cc

@@ -94,39 +94,31 @@ Engine::writeCls(std::ostream &of){
 
 
 double
-Engine::get(const std::string& key)
-  {
-
-    string var=key;
-    double z=0.;
-    string::size_type index=key.find("(");
-    if (index !=string::npos){
-      planck_assert(key.substr(key.size()-1,1)==")",key+": keyword not finishing with )");
-      var=key.substr(0,index);
-      istringstream isNum(key.substr(index+1,key.size()-index-1));
-      isNum >> z;
-      planck_assert(isNum.good(),key+": Engine canot decode z value in keyword");
-      //SP: 5sep18 previuous lines fail (don't lnow why) so back to previous method
-      //planck_assert(isNum>>z,key+": Engine canot decode z value in keyword");
-
-
-    }
-    if (var=="z_drag")  return  z_drag();
-    else if (var=="rs_drag") return  rs_drag();
-    else if (var=="f") return  get_f(z);
-    else if (var=="Dv") return  get_Dv(z);
-    else if (var=="Da") return  get_Da(z);
-    else if (var=="sigma8") return  get_sigma8(z);
-    else if (var=="H0") return  get_H0();
-    else if (var=="theta") return  theta();
-    else if (var=="tau_reio") return  get_tau_reio();
-    else if (var=="z_reio") return  get_z_reio();
-    else if (var=="H") return  get_H(z);
-    else if (var=="com_distance") return  com_distance(z);
-    else if (var=="growthD") return  get_growthD(z);
-    else { planck_assert(false,("key="+key+" not found in Engine::get()")); return -1;}
+Engine::get(const std::string& key){
+  string var=key;
+  double z=0.;
+  string::size_type index=key.find("(");
+  if (index != string::npos){
+    planck_assert(key.substr(key.size()-1,1)==")",key+": keyword not finishing with )");
+    var=key.substr(0,index);
+    istringstream isNum(key.substr(index+1,key.size()-index-2));
+    planck_assert(isNum >> z,key+": Engine cannot decode z value in keyword");
   }
-
+  if (var=="z_drag")  return  z_drag();
+  else if (var=="rs_drag") return  rs_drag();
+  else if (var=="f") return  get_f(z);
+  else if (var=="Dv") return  get_Dv(z);
+  else if (var=="Da") return  get_Da(z);
+  else if (var=="sigma8") return  get_sigma8(z);
+  else if (var=="H0") return  get_H0();
+  else if (var=="theta") return  theta();
+  else if (var=="tau_reio") return  get_tau_reio();
+  else if (var=="z_reio") return  get_z_reio();
+  else if (var=="H") return  get_H(z);
+  else if (var=="com_distance") return  com_distance(z);
+  else if (var=="growthD") return  get_growthD(z);
+  else { planck_assert(false,("key="+key+" not found in Engine::get()")); return -1;}
+}
 
 double
 Engine::undef(const char* param) const{