<html><head></head><body><div class="ydp220c2f76yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;">Hello, thanks but I resolve the former problem...besides I have a new one</div><div class="ydp220c2f76yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;">now the expresion ex that is well casted from the string is not well transformed into a derivative with diff</div><div class="ydp220c2f76yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><br></div><div class="ydp220c2f76yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><span> parser reader;<br> e = reader(ramaPrim[i]);<br></span><div><span> cout<<"ex="<<e<<" diff:"<<e.diff(r).subs(r==Pi)<< " i="<<i<<endl;<br></span></div><div><br></div><div><div>e is well printed and is a function of r but its derivative is cero!</div><div>What is happening here</div><div>Thanks<br></div><span></span></div></div></body></html>