puting an element from many areas inside one big array?

I made this random sentance generating program it generates 20 sentences and it's is currently working like it's supposed to. I need to change comething though. Instead of printing out the array elements individually, I am supposed to concatenate them into one array named that looks like this

Code:

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char sentence[80]

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I don't know how to go about doing that though. I need to concatenante all of the elements in one array with spaces in between the words, a capital letter at the begining and a period at the end. I tried playing around with strcat, but didn't have much luck.

Code:

---

#include <iostream>
#include <ctime>

using namespace std;

int main()
{


srand(time(NULL));

char *article[]= {"the", "a", "one", "some", "any"};
char *noun[] = {"boy", "girl", "dog", "town", "car"};
char *verb[] = {"drove", "jumped", "ran", "walked", "skipped"};
char *preposition[]= {"to", "from", "over", "under", "on"};

for(int i = 1; i <21; i++)
{
int articleRand = rand() % 5 ;
int nounRand= rand() % 5 ;
int verbRand = rand() % 5 ;
int prepositionRand= rand() % 5 ;
int noun2 = rand() % 5;
int article2 = rand() % 5;

cout << article[articleRand] << " " << noun[nounRand] << " "
<< verb[verbRand] << " " << preposition[prepositionRand]
<< " " << article[article2] << " " << noun[noun2] << "." << endl;
}

system("pause");

return 0;
}

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Any help would be greately appreciated!

Since you're using C style strings, strcat or strncat is probably the way to go. What did you try?

Why ARE you using char arrays for strings in a C++ program?

Code:

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ostringstream sentence;

sentence << article[articleRand];

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I guess I am using them because that's what my professor and book are asking me to do. The code I used for strcat I believe was something like this

Code:

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strcat(sentence, *article[articleRand])

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I am not exactly sure if that's what it was, but something close, I'm not next to my book or other compuer right now so I can't say for sure. Is that the best method for this? If so, my syntax is obviously wrong.

That's not exactly right, but it's close (you don't need the star there). When you get to a computer try to solve it with strcat and then if it doesn't work post that code and the problem you're having. It might just be a simple thing.

I got it to work when it's not in a loop. When it's in the loop, it acts pretty crazy then crashes. I tried moving some declarations around but that didn't seem to do much.

Code:

---

#include <iostream>
#include <cstring>

using namespace std;

int main()
{


char sentence[80];
srand(time(NULL));

char *article[]= {"the", "a", "one", "some", "any"};
char *noun[] = {"boy", "girl", "dog", "town", "car"};
char *verb[] = {"drove", "jumped", "ran", "walked", "skipped"};
char *preposition[]= {"to", "from", "over", "under", "on"};



for(int i = 1; i <21; i++)
{

int articleRand = rand() % 5 ;
int nounRand= rand() % 5 ;
int verbRand = rand() % 5 ;
int prepositionRand= rand() % 5 ;
int noun2 = rand() % 5;
int article2 = rand() % 5;

strcat(sentence, article[articleRand]);
strcat(sentence, " ");
strcat(sentence, noun[nounRand]);
strcat(sentence, " ");
strcat(sentence, verb[verbRand]);
strcat(sentence, " ");
strcat(sentence, preposition[prepositionRand]);
strcat(sentence, " ");
strcat(sentence, article[article2]);
strcat(sentence, " ");
strcat(sentence, noun[noun2]);
strcat(sentence, ".");

 



cout << sentence << endl;;

}

system("pause");

return 0;
}

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I figured out that the first 3 characters in sentence must be undefined or something because it just shows these random characters there (not letters or anything, I don't really know what they are). So maybe that's why it crashes and acts funny when I put it in a loop?

I believe strcat looks for the first null character in the array to find where the current string ends. (That's how C-style strings indicate the end of the string.)

If you don't set the first character of sentence to null, then it just has garbage in there and strcat will just look until it accidentally finds a null character. Then it will append the first string after that. That's why the first few characters were garbage, because strcat thought they were part of the sentence and added the first word after them.

Every time you want to "erase" sentence, you should set the first character to '\0'.

Well if there was ever a perfect example of how NOT to use a char array, then this is it!

Explain again WHY you're playing with crummy char arrays in a C++ program.

Quote:

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Originally Posted by Salem

Well if there was ever a perfect example of how NOT to use a char array, then this is it!

Explain again WHY you're playing with crummy char arrays in a C++ program.

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I am playing with char arrays because my professor assigned this program to us and I want to get a good grade in the class. Since I'm using this char array so bad do you have any suggestions for me?

I don't see what makes this such a good demonstration of how not to use char*'s (I've certainly seen much worse code, and not just from beginners).

A couple of things:
You need to include <cstdlib> to use rand().
Your char*'s should be const char*'s.
Do what daved told you to and you should be fine.

I think it's fine here in this program, but in the future you should know that the line:
char sentence[80];
is very bad. This exact line of code is one of the number one causes of serious security flaws.

It would seem your prof's approach to teaching you to run begins with breaking your legs.

Suggestions
- make sure you initialise everything
Your first mistake was strcat() on an uninitialised char array

- make sure you count everything
Don't blindly assume that strcat can append without overrunning the array.
There are strncpy() and strncat() functions, but these also need care in their use.

Okay, I know what you guys are saying about setting the first character to null. I did that, and now my program works exactly like it's supposed to. Thank you guys for your help regarding this. Here is my code

Code:

---

#include <iostream>
#include<ctime>


using namespace std;

int main()
{


char sentence[80];

srand(time(NULL));

char *article[]= {"the", "a", "one", "some", "any"};
char *noun[] = {"boy", "girl", "dog", "town", "car"};
char *verb[] = {"drove", "jumped", "ran", "walked", "skipped"};
char *preposition[]= {"to", "from", "over", "under", "on"};



for(int i = 1; i <21; i++)
{

int articleRand = rand() % 5 ;
int nounRand= rand() % 5 ;
int verbRand = rand() % 5 ;
int prepositionRand= rand() % 5 ;
int noun2 = rand() % 5;
int article2 = rand() % 5;
sentence[0] = '\0';

strcat(sentence, article[articleRand]);
strcat(sentence, " ");
strcat(sentence, noun[nounRand]);
strcat(sentence, " ");
strcat(sentence, verb[verbRand]);
strcat(sentence, " ");
strcat(sentence, preposition[prepositionRand]);
strcat(sentence, " ");
strcat(sentence, article[article2]);
strcat(sentence, " ");
strcat(sentence, noun[noun2]);
strcat(sentence, ".");

 sentence[0] = toupper(sentence[0]);



cout << sentence << endl;;

}

system("pause");

return 0;
}

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Quote:

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Originally Posted by nick753

I am playing with char arrays because my professor assigned this program to us and I want to get a good grade in the class. Since I'm using this char array so bad do you have any suggestions for me?

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Have you actually asked if you are allowed to use std::string or not?
Sometimes you may be given bad code, but you are allowed to "fix" it.