Solved

Posted on 2004-08-30
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I am fairly new to this, and cannot figure out why I get this error.
Here is the whole function with the error in it.

int random(int top){
int i, digit;
int numdigits = 0;
while(top >= 1){
top = top / 10;
numdigits++;
}
char toparr[7];
itoa(top, toparr, 10);
for(i = 0; i <= numdigits; i++){
-->   digit = atoi(toparr[i]);   <-- this line gives error, invalid  conversion from `char' to `const char*'
int prev = i-1;
int randnum;
if(i != 1 && result[prev] == toparr[prev]){
randnum = digit;
}else{
randnum = 9;
}
srand(static_cast<unsigned>(time(0)));
int random_integer;
for(int num = 0; num < 250; num++){
rand();
}
result[i] = int(randnum * rand()/(RAND_MAX+1.0));
}
int r = atoi(result);
return (r);
}
0
Question by:yajoros
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LVL 22

Expert Comment

ID: 11936804
You can't do an atoi of a single character that way.

Try   digit = toparr[ i ] - '0';

0

LVL 86

Expert Comment

ID: 11937602
Just use

digit = atoi(&toparr[i]);

since you want to call a conversion routine with an offset into a char array, you can the index operator, but you need to be aware that it returns a 'char', thus the error message. All you have to do now is to apply the 'address operator'. BTW.

digit = atoi(toparr+i);

would work also.
0

Author Comment

ID: 11937628
if i make toparr a string, should a stringstream like this work?

stringstream dg;
dg << digit;
dg >> toparr[i];
0

LVL 86

Expert Comment

ID: 11937640
Yes, that should work, but remeber tat you should test if there's enough space available in the array to hold the input.
0

Author Comment

ID: 11937647
is there a way to define the length?
0

LVL 86

Expert Comment

ID: 11937698
For a stringstream extraction operation? Sure, e.g

dg << digit;
dg >> setprecision(number_of_bytes) >> toparr[i];

should work.
0

Author Comment

ID: 11937812
it says 'setprecision' is undefined.
0

Author Comment

ID: 11937919
and yes i just realized i had it backwards
0

LVL 86

Expert Comment

ID: 11937957
>> it says 'setprecision' is undefined.

Ooops :o)

#include <iomanip>
0

Author Comment

ID: 11938038
ok, that works, but i dont think its necessary, the max would be 7 digits.
now my problem is this:
first, here is updated code:

int random(int top){
int i, digit;
int numdigits = 0;
int top2 = top;
while(top2 >= 1){  //gets number of digits in 'top'
top2 = top2 / 10;
numdigits++;
}
cout << "top: " << top << endl;
stringstream re;
string toparr;
re << top;
re >> toparr;
cout << "toparr: " << toparr << endl;
string result;
for(i = 0; i < numdigits; i++){  //makes random number by making random individual digits with max of the corresponding digit
stringstream dg;
dg << toparr[i];
dg >> digit;
int randnum;
if(i == 1){if(result[i-1] == toparr[i-1]){randnum = digit + 1;}else{randnum = 10;}}
if(i == 2){if(result[i-1] == toparr[i-1] && result[i-2] == toparr[i-2]){randnum = digit + 1;}else{randnum = 10;}}
if(i == 3){if(result[i-1] == toparr[i-1] && result[i-2] == toparr[i-2] && result[i-3] == toparr[i-3]){randnum = digit + 1;}else{randnum = 10;}}
if(i == 4){if(result[i-1] == toparr[i-1] && result[i-2] == toparr[i-2] && result[i-3] == toparr[i-3] && result[i-4] == toparr[i-4]){randnum = digit + 1;}else{randnum = 10;}}
if(i == 5){if(result[i-1] == toparr[i-1] && result[i-2] == toparr[i-2] && result[i-3] == toparr[i-3] && result[i-4] == toparr[i-4] && result[i-5] == toparr[i-5]){randnum = digit + 1;}else{randnum = 10;}}
if(i == 6){if(result[i-1] == toparr[i-1] && result[i-2] == toparr[i-2] && result[i-3] == toparr[i-3] && result[i-4] == toparr[i-4] && result[i-5] == toparr[i-5] && result[i-6] == toparr[i-6]){randnum = digit + 1;}else{randnum = 10;}}
srand(static_cast<unsigned>(time(0)));
int random_integer;
for(int num = 0; num < (9*i); num++){
rand();
}
char randomch;
int random = int(randnum * rand()/(RAND_MAX+1.0));
stringstream rr;
rr << random;
rr >> result[i];
cout << endl << "digit from array: " << digit << " toparr: " << toparr[i] << endl;
cout << "range for digit: " << randnum << endl;
cout << "result in array[" << i << "] " << result[i] << endl;
cout << "cumulative result: " << result << endl;
}
stringstream rs;
int finalresult;
rs << result;
rs >> finalresult;
return (finalresult);
}

i made it display various variables every time so i can't pinpoint the problem.
i can get every digit to be recorded into record[i], but when i display the contents of record, i get nothing.
any ideas?
thanks a lot for all your help btw
0

Author Comment

ID: 11938041
i mean result, not record sorry
0

LVL 39

Expert Comment

ID: 11940271
It doesn't work because of that:

>>>        rr >> result[i];

You defined result as

string result;

It's an empty string and result[i] isn't valid because of that.

Do that:

string result;
for (int j = 0; j < numdigits; ++j)
{
result += '0';
}

Then it should work.

Regards, Alex
0

LVL 39

Accepted Solution

itsmeandnobodyelse earned 130 total points
ID: 11940425
Ok, i checked your function and reduced the code to that:

int random(int top)
{
int i, digit;
int numdigits = 0;
int top2 = top;
while(top2 >= 1){  //gets number of digits in 'top'
top2 = top2 / 10;
numdigits++;
}
cout << "top: " << top << endl;
stringstream re;
string toparr;
re << top;
re >> toparr;
cout << "toparr: " << toparr << endl;
string result;
for (int j = 0; j < numdigits; ++j)
result += '0';
//makes random number by making random individual digits with max of the corresponding digit
srand(static_cast<unsigned>(time(0)));
for(i = 0; i < numdigits; i++)
{
digit = toparr[i];
int randnum = rand();  // init randnum for case i == 0
if (i > 0)
{
// the following covers all six if statements you had
// however, it's not very likely that the condition ever will be true
// in several tests i always got 10
if (result.substr(0, i) == toparr.substr(0, i))
randnum = digit + 1;
else
randnum = 10;
}
// int random_integer;
// what is that for???
for(int num = 0; num < (9*i); num++)
{
rand();
}
// char randomch;
int random = int(randnum * rand()/(RAND_MAX+1.0));
// by using stringstream you'll get the first digit while i take the last digit by that
result[i] = static_cast<char>(random%10 + '0');
cout << endl << "digit from array: " << digit << " toparr: " << toparr[i] << endl;
cout << "range for digit: " << randnum << endl;
cout << "result in array[" << i << "] " << result[i] << endl;
cout << "cumulative result: " << result << endl;
}
stringstream rs;
int finalresult;
rs << result;
rs >> finalresult;
return (finalresult);
}

However, i doubt that all that code gives any significant advantage to calling

srand(time(0));
int r = rand();

beside that you get different numbers.

Regards, Alex

0

Author Comment

ID: 11946759
excellent, thank you.  and yes, i guess i am messy, i wnet through a lot of snippets of code and sometimes left stuff behind.
0

Author Comment

ID: 11946776
the srand is supposed to initialize the random thing, and by using the current time, it gets a different seed every time you run it, just to make it more random.  even though for this purpose its not really necessary.
0

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