Can't seem to figure out what I'm doing wrong here. Any suggestions would be greatly appreciated. Code and error below.
#include <cs50.h>
#include <stdio.h>
int main(void)
{
int blocks = 0;
do
{
printf("%d\n", blocks);
int blocks = get_int();
}
while (blocks < 0 || blocks > 23);
}
mario.c:10:13: error: declaration shadows a local variable [-Werror,-Wshadow]
int blocks = get_int();
^
mario.c:6:9: note: previous declaration is here
int blocks = 0;
^
mario.c:10:13: error: unused variable 'blocks' [-Werror,-Wunused-variable]
int blocks = get_int();
^
2 errors generated.
make: *** [mario] Error 1
Looks like you are declaring twice:
int blocks = 0; //<--- First here
int blocks = get_int(); //<--- Then here
Try changing the second line to:
blocks = get_int();
I think you have to first say int blocks = get_int()
and then go to the
do
{
printf....
}
my reasoning is that in your code you already gave int blocks a fixed integer, 0.
Right now i'm also stuck on this problem
Related
I am fairly new to C++. I was practicing some ds,algo.This code looks fine to me, but I am getting some error about function not taking 2 arguments. Though I get some error asked in stackoverflow none of the cases match my problem.
#include <iostream>
#include <algorithm>
int ropecutting(int n, int *cuts){
if (n == 0)
return 0;
if (n < 0)
return -1;
int res = std::max(ropecutting(n-cuts[0], cuts), ropecutting(n-cuts[1], cuts), ropecutting(n-cuts[2], cuts));
if(res == -1) return -1;
return res+1;
}
int main(){
int n, cuts[3];
std::cin >> n;
for(int i = 0; i < 3; i ++)
std::cin >> cuts[i];
std::cout << ropecutting(n, cuts);
}
The error I get is,
main.cpp
G:\software_installation\Visual Studio Community 2017\VC\Tools\MSVC\14.16.27023\include\xlocale(319): warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc
G:\software_installation\Visual Studio Community 2017\VC\Tools\MSVC\14.16.27023\include\algorithm(5368): error C2064: term does not evaluate to a function taking 2 arguments
G:\software_installation\Visual Studio Community 2017\VC\Tools\MSVC\14.16.27023\include\algorithm(5367): note: see reference to function template instantiation 'const _Ty &std::max<int,int>(const _Ty &,const _Ty &,_Pr) noexcept(<expr>)' being compiled
with
[
_Ty=int,
_Pr=int
]
G:\software_installation\Visual Studio Community 2017\VC\Tools\MSVC\14.16.27023\include\algorithm(5368): error C2056: illegal expression
Wishing someone would point me out in the right direction. Thank you.
Of the overloads of std::max, the only one which can be called with three arguments is
template < class T, class Compare >
constexpr const T& max( const T& a, const T& b, Compare comp );
So since it receives three int values, that function is attempting to use the third value as a functor to compare the other two, which of course doesn't work.
Probably the simplest way to get the maximum of three numbers is using the overload taking a std::initializer_list<T>. And a std::initializer_list can be automatically created from a braced list:
int res = std::max({ropecutting(n-cuts[0], cuts),
ropecutting(n-cuts[1], cuts),
ropecutting(n-cuts[2], cuts)});
I am new to coding and I keep getting stuck in the first few lines of code and I cannot figure out why. This is what I have so far:
#include <stdio.h>
#include <cs50.h>
int main(void);
int n;
{
printf("Minute: ");
int n = get_int();
}
I am getting this message when I try to compile the code:
What did I do wrong?
You're trying to call the main function. You should only define it. It will be called when the program is executed (it is the "entry point").
To define it, remove the semicolon after
int main(void)
You can also remove that void keyword
Then move that line down, between
int n; and the { that comes after it
Additionally, you're declaring the n variable twice. After you fix the first error, the compiler will complain about this one. Remove one of the declarations then.
You should remove the semicolon after int main(void) and move the variable declaration for n within the braces. Here is the correct code below.
#include <stdio.h>
#include <cs50.h>
int main(void)
{
int n;
printf("Minute: ");
int n = get_int();
}
I'm learning to programming using pthread for a adder program, after reference several codes still don't get how to pass multiple arguments into a thread using a struct, here is my buggy program:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
typedef struct s_addition {
int num1;
int num2;
int sum;
} addition;
void *thread_add_function (void *ad)
{
printf ("ad.num1:%d, ad.num2:%d\n",ad.num1, ad.num2);
ad.sum = ad.num1 + ad.num2;
pthread_exit(0);
}
int main()
{
int N = 5;
int a[N], b[N], c[N];
srand (time(NULL));
// fill them with random numbers
for ( int j = 0; j < N; j++ ) {
a[j] = rand() % 392;
b[j] = rand() % 321;
}
addition ad1;
pthread_t thread[N];
for (int i = 0; i < N; i++) {
ad1.num1 = a[i];
ad1.num2 = b[i];
printf ("ad1.num1:%d, ad1.num2:%d\n",ad1.num1, ad1.num2);
pthread_create (&thread[i], NULL, thread_add_function, &ad1);
pthread_join(thread[i], NULL);
c[i] = ad.sum;
}
printf( "This is the result of using pthread.\n");
for ( int i = 0; i < N; i++) {
printf( "%d + %d = %d\n", a[i], b[i], c[i]);
}
}
But when compiling I got the following error:
vecadd_parallel.c:15:39: error: member reference base type 'void *' is not a
structure or union
printf ("ad.num1:%d, ad.num2:%d\n",ad.num1, ad.num2);
I tried but still cannot get a clue, what I am doing wrong with it?
Seems like you have a problem with trying to access the members of a void datatype.
You will need to add a line to cast your parameter to thread_add_function to the correct datatype similar to addition* add = (addition*)ad;, and then use this variable in your function (note that you also have to change you r .'s to -> because it's a pointer)
You also should only pass data to threads that was malloc()'d, as stack allocated data may not be permanent. It should be fine for the current implementation, but changes later could easily give strange, unpredictable behaviour.
i am trying to use dgels function of lapacke:
when i use it with malloc fucntion. it doesnot give correct value.
can anybody tell me please what is the mistake when i use malloc and create a matrix?
thankyou
/* Calling DGELS using row-major order */
#include <stdio.h>
#include <lapacke.h>
#include <conio.h>
#include <malloc.h>
int main ()
{
double a[3][2] = {{1,0},{1,1},{1,2}};
double **outputArray;
int designs=3;
int i,j,d,i_mal;
lapack_int info,m,n,lda,ldb,nrhs;
double outputArray[3][1] = {{6},{0},{0}};*/
outputArray = (double**) malloc(3* sizeof(double*));
for(i_mal=0;i_mal<3;i_mal++)
{
outputArray[i_mal] = (double*) malloc(1* sizeof(double));
}
for (i=0;i<designs;i++)
{
printf("put first value");
scanf("%lf",&outputArray[i][0]);
}
m = 3;
n = 2;
nrhs = 1;
lda = 2;
ldb = 1;
info = LAPACKE_dgels(LAPACK_ROW_MAJOR,'N',m,n,nrhs,*a,lda,*outputArray,ldb);
for(i=0;i<m;i++)
{
for(j=0;j<nrhs;j++)
{
printf("%lf ",outputArray[i][j]);
}
printf("\n");
}
getch();
return (info);
}
The problem may come from outputArray not being contiguous in memory. You may use something like this instead :
outputArray = (double**) malloc(3* sizeof(double*));
outputArray[0]=(double*) malloc(3* sizeof(double));
for (i=0;i<designs;i++){
outputArray[i]=&outputArray[0][i];
}
Don't forget to free the memory !
free(outputArray[0]);
free(outputArray);
Edit : Contiguous means that you have to allocate the memory for all values at once. See http://www.fftw.org/doc/Dynamic-Arrays-in-C_002dThe-Wrong-Way.html#Dynamic-Arrays-in-C_002dThe-Wrong-Way : some packages, like fftw or lapack require this feature for optimization. As you were calling malloc three times, you created three parts and things went wrong.
If you have a single right hand side, there is no need for a 2D array (double**). outputArray[i] is a double*, that is, the start of the i-th row ( row major). The right line may be outputArray[i]=&outputArray[0][i*nrhs]; if you have many RHS.
By doing this in your code, you are building a 3 rows, one column, that is one RHS. The solution, is of size n=2. It should be outputArray[0][0] , outputArray[1][0]. I hope i am not too wrong, check this on simple cases !
Bye,
copying some data I had for working boost threads, I implemented the following code below.
I get the error C:\dev\default threads_threads.cpp|18|error: invalid conversion from 'void ()(void)' to 'unsigned int (attribute((stdcall)) )(void)' [-fpermissive]|
but... the commented lines are what was recommended, and a comment explains the error I got.
it turns out _beginThreadEx is highly recommended, but poorly documented (as in tutorials) on the web
#include <iostream>
#include <process.h>
void myThread(void *data)
{
//C:\dev\default threads\_threads.cpp|6|error: invalid conversion from 'int*' to 'int' [-fpermissive]|
//int x = static_cast<int*>(data);
int *x = (int*)data;
std::cout << "Hellow World! " << x;
}
int main()
{
int x = 10;
_beginthreadex(NULL, 0, myThread, &x, 0, NULL);
while(true);
}
You have to declare x as pointer anyway:
int *x = static_cast<int*>(data);
both _beginthread and _beginthreadex are documented here: http://msdn.microsoft.com/en-us/library/kdzttdcb(v=vs.80).aspx
According to the declaration of _beginthreadex() your myThread() function should be declared like this:
unsigned __stdcall myThread(void *data);