Can't construct a mpz_class of a string

[Daniel L ännström]

The manual is saying: "void mpz_class::mpz_class (const string& s)". Way doesn't this work? mpz_class tal = std::string("12319238"); 

I got this error by GCC: 
problem3.cpp: In function `int main()':
problem3.cpp:49: conversion from `std::string' to non-scalar type `
   __gmp_expr<__gmpz_value, __gmpz_value>' requested

Does anybody knows what I'm doing wrong? And I know that my english sucks. :)

// Danne
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