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// Input expression containing variable 'x' and compute its derivative
// with respect to 'x'.
// Example from the tutorial (chapter Input/Output, section `Expression
// input').
#include <iostream>
#include <string>
#include <stdexcept>
#ifdef IN_GINAC
#include "ginac.h"
#else
#include <ginac/ginac.h>
#endif
using namespace std;
using namespace GiNaC;
int main()
{
cout << "Enter an expression containing 'x': " << flush;
parser reader;
try {
ex e = reader(cin);
symtab table = reader.get_syms();
symbol x = table.find("x") != table.end() ?
ex_to<symbol>(table["x"]) : symbol("x");
cout << "The derivative of " << e << " with respect to x is ";
cout << e.diff(x) << "." << endl;
} catch (exception &p) {
cerr << p.what() << endl;
}
}
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