int jecislo(char* retezec) //test, zda dany retezec obsahuje cislo
{
    long double prevod;
    char *pointer;

    prevod=strtold(retezec,&pointer);

    if(*pointer!='\0')
        return neni_cislo;

    else
        {
            int i, delka=strlen(retezec);

            for(i=0;i<delka;i++)
                {
                if(retezec[i]=='.')
                return desetinne_cislo;
                }
        }

    return cele_cislo;
}