Validate FLOAT data entry [duplicate]

Question

Validate FLOAT data entry [duplicate]

Navigation

#1 by (1 votes)

2

I need the program to accept only decimal numbers. The one I did is fine, only accepts decimals, but if you enter for example -23.45jdhsdj . The numbers if you save them, although you ignore the letters and it should not be like that. You should reject a number that contains lyrics in any part of it.

Here I leave what I have achieved so far:

#include <iostream>
#include <string>
#include <cctype>
#include <cstdlib>

using namespace std;
bool funciondecimal(string);
int main()
{
string numero;
bool repite=true;
do{
  cout<<"Dijite el numero: ";
  cin>>numero;

   if(!funciondecimal(numero)){
    cout<<"tiene punto decimal"<<endl;
    repite=false;
   }else{
    cout<<"No tiene punto decimal"<<endl;
   }
}while(repite);
return 0;
}
bool funciondecimal(string numero){
  bool resp= true;
   for(int contador=1;contador<=numero.size();contador++){
    if(numero[contador-1]=='.'|| numero[contador-1]==','){
            resp=false;
            break;
    }
}
return resp;
}

PS: I was asked the question as a duplicate, but the one that currently exists and has a solution is for integers and I need it only for FLOAT, thanks Here the solution for integers in Stack Overflow

Here I leave the last improvement I made: no longer allows letters but still allowing characters (! @ # $% ^ & amp? *? < +), if someone has an idea of how to solve it would be great, thanks

#include <iostream>
#include <string>
#include <cctype>
#include <cstdlib>

using namespace std;
bool funciondecimal(string);
int main()
{
string numero;
bool repite=true;
do{
cout<<"Dijite el numero: ";
cin>>numero;

if(funciondecimal(numero)){
    cout<<"tiene punto decimal"<<endl;
    repite=false;
}else{
    cout<<"No tiene punto decimal"<<endl;
}
}while(repite);
return 0;
}
bool funciondecimal(string numero){
bool resp= false;
 for(int contador=1;contador<=numero.size();contador++){
    if((numero[contador-1]=='-'|| numero[contador-1]=='+')  &&  (numero[contador]==','|| numero[contador]=='.')){
            resp=true;
            break;
    }
 }
 for (int contador2=1;contador2<=numero.size();contador2++){
        if((numero[contador2]>='0' && numero[contador2]<='9') &&   (numero[contador2]==','|| numero[contador2]=='.')){
            resp=true;
        }
 }
 for(int contador3=1;contador3<=numero.size();contador3++){
        if(numero[contador3-1]==','|| numero[contador3-1]=='.'){
            resp=true;
        }
 }
 for(int contador4=1;contador4<=numero.size();contador4++){
        for(int letra='a';letra<='z';letra++){
                if(numero[contador4-1]==letra){
                  resp=false;
                  break;
                }
        }
        for(int letra2='A';letra2<='Z';letra2++){
            if(numero[contador4-1]==letra2){
               resp=false;
               break;
               }
        }
   // if(numero[contador4-1]=='a'){
     //   resp=false;
       // break;
    //}
 }
return resp;
}

c++ float

asked by Ali Rash 20.09.2018 в 08:29

source

1 answer

Bubble sorting in vue.js Problem in insert SQLite

score 1 · Accepted Answer

From C ++ 11 you have the std::stof() function available to you, which makes exactly what you are looking for:

bool EsFloat(std::string const& numero)
{
  bool toReturn = false;

  try
  {
    std::size_t pos = 0;
    std::stof(numero,&pos);

    // Verificamos que se ha procesado todo el contenido de numero 
    toReturn = ( pos == numero.length() );
  }

  catch(std::exception const&)
  {
    // 1234e1000 -> std::out_of_range      
    // HOLA      -> std::invalid_argument
  }

  return toReturn;
}

Going back to previous standards, we found a somewhat coarser version called strtof (instead of working with std::string use char* and, moreover, this function does not throw exceptions):

#include <cmath> 
bool EsFloat(std::string const& numero)
{
  bool toReturn = false;

  char* pos = 0;
  float result = std::strtof(numero.c_str(),&pos);

  // Verificamos que se ha procesado todo el contenido de numero  
  toReturn = (pos == &numero[numero.length()] && result);

  // Y comprobamos además que el numero resultante es valido
  toReturn &= (result != std::HUGE_VAL);

  return toReturn;
}