Title. I want to loop over string (char *) arrays. Size is known, but I have to pass them through a function so they will invariable become char** and I wonder how to do that.
#Looping over string arrays
cunning tree
odd wadiBOT
whole slate
void foo(const char*const*a,size_t l);// doesn't modify the array nor the strings pointed to in the array
const char*a[]={"abc","def","ghi"};
foo(a,sizeof(a)/sizeof(*a));
something like that?
you could then loop over the array using the size in the function
oblique flare
```c
void foo(const char*const*a,size_t l);// doesn't modify the array nor the s...
How does this bind btw? Is this an array of char pointers, or a pointer to char arrays?
In case it wasn't obvious, talking about this: char *a[].
cunning tree
```c
void foo(const char*const*a,size_t l);// doesn't modify the array nor the s...
It's more like foo(char ** a) right now, though the strings aren't modified
whole slate
How does this bind btw? Is this an array of char pointers, or a pointer to char ...
*a[] is equivalent to *(a[])
cunning tree
And I'm initializing (probably wrongly) the array like char a[][4] = {"abc", "def", "ghi"}
whole slate
`*a[]` is equivalent to `*(a[])`
the precedence is equivalent to that of the operators, the expression *a[N] is equivalent to *(a[N])
cunning tree
Size of the strings is known beforehand
oblique flare
`*a[]` is equivalent to `*(a[])`
alright, so a is a pointer to char arrays? (Just to verify I'm not misunderstanding this here)
whole slate
alright, so `a` is a pointer to char arrays? (Just to verify I'm not misundersta...
a is an array of pointers
whole slate
Sry for the distraction but what would `(*a)[]` be then?
the opposite, a pointer to an array
molten warren
whole slate
And I'm initializing (probably wrongly) the array like `char a[][4] = {"abc", "d...
this won't decay to char**, since a isn't an array of pointers here, it is an array of arrays of 4 characters
it would decay to char(*)[4]
when you take a pointer to the first element it is really pointing to the array of 4 characters
cunning tree
Yeah, but I can not create a char(*)[4] type to use in the function argument, can I?
whole slate
;compile
#include<stdio.h>
void foo(char(*a)[4],size_t l){
for(size_t i=0;i<l;++i){
puts(a[i]);
}
}
int main(void){
char a[][4]={"abc","def","ghi"};
foo(a,sizeof(a)/sizeof(*a));
}
frank oakBOT
whole slate
here is an example of passing a char(*)[4] as an argument to a function that iterates over the array
cunning tree
Hmm
And how would that look like as a pointer to pointers **a
Both the initializing and using in func
whole slate
a pointer to a pointer, points at a pointer
you would need to make a new array that was an array of pointers if you wanted an array of pointers
cunning tree
char ** a;
for(size_t i=0; i<l; ++i){
*a ++;
for(size_t j = 0; j < SIZE; ++j) *a[i] = val;
}```?
whole slate
look at my original example:
const char*a[]={"abc","def","ghi"};
a is an array of pointers, so taking the address of the first element will point at the first pointer
if you wanted to make an array of pointers for
char a[][4]={"abc","def","ghi"};
then there would need to be a new array which contained a pointer to the first character of each array
e.g.
char*p[sizeof(a)/sizeof(*a)];
for(size_t i=0;i<sizeof(a)/sizeof(*a);++i){
p[i]=a[i];
}
I'm applying Cunningham's law
Let me try
Great, it works
Hopefully I'm not going into pointer land again
Thanks a lot
cunning tree
!solved