Here I need to write a function which is called from main method with integer array as a parameter please give me example.
In below example parameter are int type.
Note : please tell this is correct way to do this or not...
#import <Foundation/Foundation.h>
void displayit (int);
int main (int argc, const char * argv[])
{
#autoreleasepool {
int i;
for (i=0; i<5; i++)
{
displayit( i );
}
}
return 0;
}
void displayit (int i)
{
int y = 0;
y += i;
NSLog (#"y + i = %i", y);
}
Thanks in advance....
I tried out these, please check.
#import <Foundation/Foundation.h>
void displayit (int array[], int len);
int main (int argc, const char * argv[])
{
#autoreleasepool {
int array[]={1,2,3};
displayit( array, 3 );
}
return 0;
}
void displayit (int array[], int len)
{
for(int i=0;i<len;i++){
NSLog(#"display %d : %d",i,array[i]);
}
}
The out put is:
2014-10-30 14:09:32.017 OSTEST[32541:77397] display 0 : 1
2014-10-30 14:09:32.018 OSTEST[32541:77397] display 1 : 2
2014-10-30 14:09:32.018 OSTEST[32541:77397] display 2 : 3
Program ended with exit code: 0
I used another parameter len to avoid boundary beyond.
If the array is a global, static, or automatic variable (int array[10];), then sizeof(array)/sizeof(array[0]) works. Quoted From Another Question
Related
I'm trying to solve Problem 10 in Project Euler, and while I thought I had it, its saying my answer is incorrect. The question is as follows:
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the primes below two million.
And my code:
int sum;
#interface Prime : NSObject
-(BOOL)isPrime:(int)arg1;
#end
#implementation Prime
-(BOOL)isPrime:(int)arg1 {
if (arg1 == 1) {
NSLog(#"Given 1");
return NO;
}
for (int i = 2; i < arg1; i++) {
if (arg1 % i == 0) {
return NO;
}
}
sum += arg1;
return YES;
}
#end
int main(int argc, const char * argv[])
{
#autoreleasepool {
Prime* primeObject = [[Prime alloc] init];
for (int i = 0; i < 2000000; i++) {
[primeObject isPrime:i];
}
NSLog(#"Sum of primes is %i", sum);
}
}
This code outputs 'Sum of primes is 1179908154' which Project Euler says is incorrect. Help?
The problem is that the sum does not fit into a 32-bit integer. You should use long long instead.
Just a guess, you should try to:
Initialise the sum variable to 0.
Try not to use a global variable like sum that can be accessed from anywhere, in this case do the sum in the main loop instead of in the isPrime method.
Maybe that'll give you the right answer.
You are using int for getting result, so it is wrong.
I'm using long int instead, that is enough for this case.
Here is my code, and it works fine:
int inputNumber = 2000000;
long int result = 0;
for (int i = 2; i < inputNumber; i++) {
BOOL isPrime = YES;
for (int j = 2; j <= sqrt(i); j++) {
if (i%j==0) {
isPrime = NO;
break;
}
}
if (isPrime) {
result += i;
}
}
Result is: 142913828922
I'm completely new to Objective C and I'm trying to use it to wrap a C-library. I have a main.m wrap.m and wrap.h files. From what I gather in the header file I included #interface and in the source file I will include #implementation However I'm not really understanding what to include in each of them. Right now my main file is:
int copy_data(struct archive *ar, struct archive *aw) {
for (;;) {
const void *buff;
size_t size;
off_t offset;
int r = archive_read_data_block(ar, &buff, &size, &offset);
if (r == ARCHIVE_EOF)
return (ARCHIVE_OK);
archive_write_data_block(aw, buff, size, offset);
}
}
int main(int argc, const char * argv[])
{
#autoreleasepool {
struct archive *a;
struct archive *ext;
struct archive_entry *entry;
int flags;
int r;
/* Select which attributes we want to restore. */
flags = ARCHIVE_EXTRACT_TIME;
flags |= ARCHIVE_EXTRACT_PERM;
flags |= ARCHIVE_EXTRACT_ACL;
flags |= ARCHIVE_EXTRACT_FFLAGS;
a = archive_read_new();
archive_read_support_format_all(a);
archive_read_support_compression_all(a);
ext = archive_write_disk_new();
archive_write_disk_set_options(ext, flags);
archive_write_disk_set_standard_lookup(ext);
r = archive_read_open_filename(a, argv[1], 10240);
for (;;) {
r = archive_read_next_header(a, &entry);
if (r == ARCHIVE_EOF)
break;
r = archive_write_header(ext, entry);
if (archive_entry_size(entry) > 0) {
copy_data(a, ext);
}
archive_write_finish_entry(ext);
}
archive_read_close(a);
archive_read_free(a);
archive_write_close(ext);
archive_write_free(ext);
NSLog(#"No Issues");
}
return 0;
}
So far what I'm getting in my wrap.h file is:
typedef struct{
int *a;
int *ext;
}archive;
#interface main : NSObject
#property int flags;
#property int r;
I don't know if that is close to what I need to do, and I'm getting errors on my ARCHIVE_EXTRACT saying they are undeclared identifiers which I assume also have to go into my wrap.h file but I'm not sure how to do that. Any help at all would be appreciated!
If you start your project in Xcode using the CommandLineTool template, you can select your language to be "C" or "C++", so you wouldn't have to mess with Objective-C at all.
As for the .h file that you currently have, don't do "#property" or "#interface" for "main". "main" is a C style function and not an Objective-C thing.
If you are actually interested in an objectivec solution, follow Michael Dautermann's instructions to start a new Command Line project but instead of Type C use the Foundation option. This will give you a working main (just a regular c function). Then select new->objective c class to create your wrap.h/wrap.m. In the wrap.h you will pretty much exclusively be declaring your own objectivec public wrapper methods. In the wrap.m, you'll be importing what you want to wrap, and defining your wrapper functions.
//
// main.m
//
#import <Foundation/Foundation.h>
#import "wrap.h"
int main(int argc, const char * argv[])
{
#autoreleasepool {
[wrap wrappedStuff];
}
return 0;
}
//
// wrap.h
//
----------
#import <Foundation/Foundation.h>
#interface wrap : NSObject
+ (void)wrappedStuff;
#end
//
// wrap.m
//
#import "wrap.h"
#include "WhatImWrapping.h"
#implementation wrap
int copy_data(struct archive *ar, struct archive *aw) {
for (;;) {
const void *buff;
size_t size;
off_t offset;
int r = archive_read_data_block(ar, &buff, &size, &offset);
if (r == ARCHIVE_EOF)
return (ARCHIVE_OK);
archive_write_data_block(aw, buff, size, offset);
}
}
+ (void)wrappedStuff
{
struct archive *a;
struct archive *ext;
struct archive_entry *entry;
int flags;
int r;
/* Select which attributes we want to restore. */
flags = ARCHIVE_EXTRACT_TIME;
flags |= ARCHIVE_EXTRACT_PERM;
flags |= ARCHIVE_EXTRACT_ACL;
flags |= ARCHIVE_EXTRACT_FFLAGS;
a = archive_read_new();
archive_read_support_format_all(a);
archive_read_support_compression_all(a);
ext = archive_write_disk_new();
archive_write_disk_set_options(ext, flags);
archive_write_disk_set_standard_lookup(ext);
r = archive_read_open_filename(a, argv[1], 10240);
for (;;) {
r = archive_read_next_header(a, &entry);
if (r == ARCHIVE_EOF)
break;
r = archive_write_header(ext, entry);
if (archive_entry_size(entry) > 0) {
copy_data(a, ext);
}
archive_write_finish_entry(ext);
}
archive_read_close(a);
archive_read_free(a);
archive_write_close(ext);
archive_write_free(ext);
NSLog(#"No Issues");
}
#end
I'm doing a tutorial from this book: "Objective-C 2.0 Essentials 3rd edition" by Neil Smyth. I have tried repeatedly but keep getting the same "Expected expression" error even though the books version claims to run. I've checked way too many times and my version is exactly the same as the books. Please, can someone help me. Code below:
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[]) {
#autoreleasepool {
int x;
int j = 54321;
for (x = 0; x < 10; x++) {
}
int j = x + 10;
NSLog (#"Variable j in for loop is %i", j);
NSLog (#"Variable j outside for loop is %i", j); /* I GET AN ERROR STATING " EXPECTED EXPRESSION HERE*/
}
return 0;
}
The line
NSLog (#"Variable j outside for loop is %i", j);
contains a lot of invisible characters (UTF-8 sequence EF BF BC = OBJECT REPLACEMENT CHARACTER) between the Tab and the "NSLog".
Deleting and rewriting that line should help.
OP's code opened in hexa editor:
Format your code better; if you do the misplaced } in the code becomes obvious:
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[]) {
#autoreleasepool {
int x;
int j = 54321;
for (x = 0; x < 10; x++) {
int j = x + 10;
NSLog (#"Variable j in for loop is %i", j);
}
 NSLog (#"Variable j outside for loop is %i", j);
}
return 0;
}
EDIT The invisible characters as pointed out by #MartinR are also an issue (that I didn't notice). So there are two errors in your code.
Block variable in objective-c is a reference and I learned from somewhere infer that following code may be transformed by compiler to another form.
Original code:
typedef int (^block_type)();
block_type create_k(int i)
{
block_type block = ^(){
return i;
};
//[block copy];
return block;
}
Generated Code:
typedef void (*generic_invoke_funcptr)(void *, ...);
struct __block_literal {
void *isa;
int flags;
int reserved;
generic_invoke_funcptr invoke;
struct __block_descriptor_tmp *descriptor;
const int captured_i;
};
static const struct __block_descriptor_tmp {
unsigned long reserved;
unsigned long literal_size;
/* no copy/dispose helpers needed */
} __block_descriptor_tmp = {
0UL, sizeof(struct __block_literal)
};
// ^int (void) { return i; }
int __create_k_block_invoke_(struct __block_literal *bp) {
return bp->captured_i;
}
typedef int (*iv_funcptr)(struct __block_literal *);
typedef int (^block_type)();
block_type create_k(int i)
{
//block_type block = ^(){
// return i;
//};
struct __block_literal __b = {
.isa = &_NSConcreteStackBlock,
.flags = BLOCK_HAS_DESCRIPTOR,
.reserved = 0,
.invoke = (generic_invoke_funcptr)__f_block_invoke_,
.descriptor = &__block_descriptor_tmp,
.captured_i = i
};
struct __block_literal *block = &__b;
return block;
}
So |_b| in stack and block is only a reference to |_b|. If |create_k| return |block|, the receiver only get a invalid address.
But
int main(int argc, const char *argv[])
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
printf("%d\n", create_k(40)());
[pool drain];
return 0;
}
By exec it, print |40| and |block| is a valid block. What's the matter?
My guess would be that the memory for that stack frame hasn't been zeroed yet. Try calling another function between create_k() and printf() to get some other random data in there.
Am running this C program, but instead of answering "The answer is 10", it sends back the message: "The answer is 0", even though it breaks at the right time.
Can you tell me what's wrong?
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[])
{
int i;
for(int i = 0; i < 12; i++){
printf("Checking i = %d\n", i);
if(i + 90 == i * i) {
break;
}
}
printf("The answer is %d.\n", i);
}
The problem is you have two i's.
int main (int argc, const char * argv[])
{
int i; //Declares outer i
for(int i = 0; i < 12; i++) //Declares a NEW i
{
printf("Checking i = %d\n", i);
if(i + 90 == i * i)
{
break;
}
}
printf("The answer is %d.\n", i); //Uses the outer i
}
Basic scope confusion: You have two different variables called i: One in the outer scope of the main function body, and another, overriding one inside the for loop.
The outer variable is uninitialized, so in fact you have undefined behaviour.
What you mean to say is this:
int i;
for (i = 0; i < 12; i++)
/* ^^^^^ use existing variable! */
{
printf("Checking i = %d\n", i);
if (i + 90 == i * i)
{
break;
}
}
Could it be the extra "int"? You're declaring another instance of "i" in the for loop that goes out of scope when the loop exits.
for(int i = 0; i < 12; i++){
You're creating another i here, which hides the i outside the scope of the for loop.
Change to:
int i;
...
for (i = 0; i < 12; i++){
Because you've got two DIFFERENT variables "i" - the one in the inner scope (which you increment from 0..11), and the one in the outer scope. You print the one in the outer scope.
SOLUTION:
change "for (int i=...)" to "for (i=...)"