#include <iostream>
#include <sstream>
#include<windows.h>
//funciones***************
int tomarint();
//****************
using namespace std;
//funiones para validar
enum ConvertError
{ NoError,
Overflow,
WrongFormat
};
//---------------------------------------------------------------------------
ConvertError ToInt( std::istream& stream, int& value )
{ ConvertError toReturn = NoError;
bool negate = false;
bool firstChar = true;
value = 0;
bool nextIteration = true;
do
{ char c = stream.peek();
if( c == EOF )
nextIteration = false;
else
{ stream.get(); // discard from the stream
if( c==' ' || c=='\n' || c=='\r' || c=='\t' )
nextIteration = false;
else if( isdigit(c) )
{ int newValue = value*10+c-'0';
if( newValue < value )
{ nextIteration = false;
toReturn = Overflow;
}
value = newValue;
}
else
{ if( (c != '-' && c != '+') || !firstChar )
{ nextIteration = false;
toReturn = WrongFormat;
}
else
negate = (c=='-');
}
}
firstChar = false;
} while(nextIteration);
if( negate )
value *= -1;
return toReturn;
}
//---------------------------------------------------------------------------
int tomar(){ int valor,resultado;
do{ stringstream stream;
string aux;
cout<<"introdusca un numero"<<endl;
cin>>aux;
if(cin.fail()) cin.ignore(); resultado=1;
stream <<aux;
resultado =ToInt(stream,valor);
}while(resultado!=0);
system("cls"); return valor;
}
int main(){ cout<<"\t\t*******************************"<<endl;
cout<<"\tprograma para saber cuando un numero es negativo o positivo que no sea 0"<<endl;
cout<<"\t\t*******************************"<<endl;
int a=0;
a=tomar();
if(a>0){ cout<<"el numero "<<a<<" es positivo"<<endl;
}else{
cout<<"el numero "<<a<<" es negativo"<<endl;
}
system("Pause");
}
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