Am I going insane? How do you input strings?

GrNxxDaY · 07-27-2002, 07:45 PM

I am having a brain fart and can't seem to get this to work right.
I want the user of my program to input a string using the standard input device. Then I want to test that string using if statements.

This is what I have so far, but for some reason I get an illegal error when I try run the .exe file.

Code:

char* input;
std::cin >> input;

am I going crazy? This seems to simple to be stuck on

should I use the <string> library header? the new/delete operators? am i really crazy?

The Dog · 07-27-2002, 07:59 PM

try this,

Code:

char* input = new char[256];
cin >> input;

GrNxxDaY · 07-27-2002, 08:10 PM

I would, but here's the problem

Code:

void getInput()  // shortened version
{
 char* input = new char[40];
 std::cin >> input;
 if (input == "err")
     doIt();
 // bunch of other if statements 
}

I can't put the delete [] thingy anywhere cause right after the user inputs a string, another function executes(based on the if statements), and the function never reaches the end. Also, this function gets called alot.

Anyone know how to slove this problem?

The Dog · 07-27-2002, 08:13 PM

then delete it when you are done with it.

GrNxxDaY · 07-27-2002, 08:15 PM

it has local scope, i'd have to delete it inside that function. but i can't because after the function uses the new keyword, it executes a different function, never returning to that orginal copy of getInput();

The Dog · 07-27-2002, 08:22 PM

then rather declare 'input' as an array.

Code:

#define MAX_ARRAY 256

void getInput()  // shortened version
{
     char* input = new char[MAX_ARRAY];
     std::cin >> input;
     if (input == "err")
          doIt();
 // bunch of other if statements 
}

you also could do it by passing the char* to each function by reference, then you could delete it in the function.

The Dog · 07-27-2002, 08:23 PM

sorry bout that should've been

Code:

#define MAX_ARRAY 256

void getInput()  // shortened version
{
     char input[MAX_ARRAY];
     std::cin >> input;
     if (input == "err")
          doIt();
 // bunch of other if statements 
}

ygfperson · 07-27-2002, 08:23 PM

Quote:

Originally posted by GrNxxDaY
it has local scope, i'd have to delete it inside that function. but i can't because after the function uses the new keyword, it executes a different function, never returning to that orginal copy of getInput();

delete doesn't have a scope, afaik. any space allocated with 'new' is global and won't unallocate unless there's a delete operator or the program closes.

Code:

if (input == "err")
     doIt();

input is a pointer. "err" is a const char pointer, pointing to a different string which might happen to have the same contents. use strcmp(), or use string classes.

//edit: you might also want to know that

Code:

char* szsomething = new char[40];
cin >> szsomething;

will input only everything up to a space. to do a whole line, use cin.getline().

The Dog · 07-27-2002, 08:32 PM

i think that ygfperson misunderstood what it is you're trying to do GrNxxDaY.

to delete a pointer, you need the pointer in the first place.

to allow doIt() to delete the pointer, you have to pass the pointer to the function.

The Dog · 07-27-2002, 08:38 PM

if you're going to new an object, and you want to delete it in another function, then you'll have to pass a pointer to it to the function.

Sebastiani · 07-27-2002, 08:42 PM

The Dog gave you the correct answer. So do:

void getInput() // shortened version
{
char input[40];
std::cin >> input;
if ( strcmp(input, "err") == 0)
doIt();
// bunch of other if statements
}

GrNxxDaY · 07-27-2002, 08:43 PM

Will this work?

Code:

void deleteDynam(char* victim)
{
 delete [] *victim;
}

void getInput()
{
 char* input = new char[40];
 deleteDynam(&input);
}

The Dog · 07-27-2002, 08:46 PM

No, but this will

Code:

void deleteDynam(char* victim)
{
   delete [] victim;
}

void getInput()
{
   char* input = new char[40];
   deleteDynam(input);
}

GrNxxDaY · 07-27-2002, 08:47 PM

ok, the heap it is. (for sure now, dont make me change my mind!)
hehe, thakns guys!!

GrNxxDaY · 07-27-2002, 09:47 PM

Code:

void deleteDynam(char* victim)
{
   delete [] victim;
}

Do I need a * before victim there? Like so...

Code:

void deleteDynam(char* victim)
{
   delete [] *victim;
}

07-27-2002, 07:45 PM	#1
GrNxxDaY Registered User Join Date: Jul 2002 Posts: 140	Am I going insane? How do you input strings? I am having a brain fart and can't seem to get this to work right. I want the user of my program to input a string using the standard input device. Then I want to test that string using if statements. This is what I have so far, but for some reason I get an illegal error when I try run the .exe file. Code: char* input; std::cin >> input; am I going crazy? This seems to simple to be stuck on should I use the <string> library header? the new/delete operators? am i really crazy? __________________ AOL: GrNxxDaY IDE: Dev-C++ Beta 5 (v4.9.4.1) Project: Eye of Sahjz (text-RPG) If you think I may need help, please IM me.
GrNxxDaY is offline

07-27-2002, 07:59 PM	#2
The Dog Registered User Join Date: May 2002 Location: Cape Town Posts: 777	try this, Code: char* input = new char[256]; cin >> input;
The Dog is offline

07-27-2002, 08:10 PM	#3
GrNxxDaY Registered User Join Date: Jul 2002 Posts: 140	I would, but here's the problem Code: void getInput() // shortened version { char* input = new char[40]; std::cin >> input; if (input == "err") doIt(); // bunch of other if statements } I can't put the delete [] thingy anywhere cause right after the user inputs a string, another function executes(based on the if statements), and the function never reaches the end. Also, this function gets called alot. Anyone know how to slove this problem? __________________ AOL: GrNxxDaY IDE: Dev-C++ Beta 5 (v4.9.4.1) Project: Eye of Sahjz (text-RPG) If you think I may need help, please IM me.
GrNxxDaY is offline

07-27-2002, 08:13 PM	#4
The Dog Registered User Join Date: May 2002 Location: Cape Town Posts: 777	then delete it when you are done with it.
The Dog is offline

07-27-2002, 08:15 PM	#5
GrNxxDaY Registered User Join Date: Jul 2002 Posts: 140	it has local scope, i'd have to delete it inside that function. but i can't because after the function uses the new keyword, it executes a different function, never returning to that orginal copy of getInput(); __________________ AOL: GrNxxDaY IDE: Dev-C++ Beta 5 (v4.9.4.1) Project: Eye of Sahjz (text-RPG) If you think I may need help, please IM me.
GrNxxDaY is offline

07-27-2002, 08:22 PM	#6
The Dog Registered User Join Date: May 2002 Location: Cape Town Posts: 777	then rather declare 'input' as an array. Code: #define MAX_ARRAY 256 void getInput() // shortened version { char* input = new char[MAX_ARRAY]; std::cin >> input; if (input == "err") doIt(); // bunch of other if statements } you also could do it by passing the char* to each function by reference, then you could delete it in the function.
The Dog is offline

07-27-2002, 08:23 PM	#7
The Dog Registered User Join Date: May 2002 Location: Cape Town Posts: 777	sorry bout that should've been Code: #define MAX_ARRAY 256 void getInput() // shortened version { char input[MAX_ARRAY]; std::cin >> input; if (input == "err") doIt(); // bunch of other if statements }
The Dog is offline

07-27-2002, 08:32 PM	#9
The Dog Registered User Join Date: May 2002 Location: Cape Town Posts: 777	i think that ygfperson misunderstood what it is you're trying to do GrNxxDaY. to delete a pointer, you need the pointer in the first place. to allow doIt() to delete the pointer, you have to pass the pointer to the function.
The Dog is offline

07-27-2002, 08:38 PM	#10
The Dog Registered User Join Date: May 2002 Location: Cape Town Posts: 777	if you're going to new an object, and you want to delete it in another function, then you'll have to pass a pointer to it to the function.
The Dog is offline

07-27-2002, 08:42 PM	#11
Sebastiani Guest Join Date: Aug 2001 Posts: 5,034	The Dog gave you the correct answer. So do: void getInput() // shortened version { char input[40]; std::cin >> input; if ( strcmp(input, "err") == 0) doIt(); // bunch of other if statements }
Sebastiani is offline

07-27-2002, 08:43 PM	#12
GrNxxDaY Registered User Join Date: Jul 2002 Posts: 140	Will this work? Code: void deleteDynam(char* victim) { delete [] victim; } void getInput() { char input = new char[40]; deleteDynam(&input); } __________________ AOL: GrNxxDaY IDE: Dev-C++ Beta 5 (v4.9.4.1) Project: Eye of Sahjz (text-RPG) If you think I may need help, please IM me.
GrNxxDaY is offline

07-27-2002, 08:46 PM	#13
The Dog Registered User Join Date: May 2002 Location: Cape Town Posts: 777	No, but this will Code: void deleteDynam(char* victim) { delete [] victim; } void getInput() { char* input = new char[40]; deleteDynam(input); }
The Dog is offline

07-27-2002, 08:47 PM	#14
GrNxxDaY Registered User Join Date: Jul 2002 Posts: 140	ok, the heap it is. (for sure now, dont make me change my mind!) hehe, thakns guys!! __________________ AOL: GrNxxDaY IDE: Dev-C++ Beta 5 (v4.9.4.1) Project: Eye of Sahjz (text-RPG) If you think I may need help, please IM me. Last edited by GrNxxDaY; 07-27-2002 at 08:51 PM.
GrNxxDaY is offline

07-27-2002, 09:47 PM	#15
GrNxxDaY Registered User Join Date: Jul 2002 Posts: 140	Code: void deleteDynam(char* victim) { delete [] victim; } Do I need a * before victim there? Like so... Code: void deleteDynam(char* victim) { delete [] victim; } __________________ AOL: GrNxxDaY* IDE: Dev-C++ Beta 5 (v4.9.4.1) Project: Eye of Sahjz (text-RPG) If you think I may need help, please IM me.
GrNxxDaY is offline

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