why array can't be assigned, like structs?
57  3254 
On Mar 7, 10:26 pm, buuuu...@gmail. com wrote:
why array can't be assigned, like structs?
Because an array can be passed to a function, or something, and the
compiler can not always know how big the array is. (This is the only
reason I can think of offhand, there are almost certainly others.)
Structures, on the other hand, always contain the same contents and so
the compiler can assign them.
Of course, if you want to assign one array to another, you can use the
memcpy() function (or memmove() if the parameters might overlap):
int array[] = {1, 2, 3, 4, 5};
int toarray[sizeof(array)/sizeof(*array)];
memcpy(toarray, array, sizeof(array));
"dwks" <ki**********@p rimus.cawrites:
On Mar 7, 10:26 pm, buuuu...@gmail. com wrote:
>why array can't be assigned, like structs?
Because an array can be passed to a function, or something, and the
compiler can not always know how big the array is. (This is the only
reason I can think of offhand, there are almost certainly others.)
Structures, on the other hand, always contain the same contents and so
the compiler can assign them.
[...]
No, an array can't be passed to a function. You can do what *looks*
like passing an array to a function, but you're really just passing a
pointer to its first element.
Arrays aren't first-class objects in C. "First-class" isn't a
well-defined concept, but basically it means that there are things you
can do with other types that you can't do with arrays. There isn't
necessarily some fundamental reason why this is so (it isn't in some
other languages); it's just the way the language happens to be
designed, influenced by its predecessors B and BCPL.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister" bu******@gmail. com wrote, On 08/03/07 05:26:
why array can't be assigned, like structs?
Because the language does not allow it.
--
Flash Gordon
dwks said:
On Mar 7, 10:26 pm, buuuu...@gmail. com wrote:
>why array can't be assigned, like structs?
Because an array can be passed to a function,
No, it can't.
or something, and the
compiler can not always know how big the array is.
The compiler knows /exactly/ how big the array is.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999 http://www.cpax.org.uk
email: rjh at the above domain, - www.
On Mar 8, 10:26 am, buuuu...@gmail. com wrote:
why array can't be assigned, like structs?
Because its the way language has been designed!
Its a feature(or liability!) inherited from the langauage B, C's
predecessor.In B arrays are called Vectors
You dont have the concept of structures in B. They are concepts
developed by C and therefore Ritchie has allowed assignment of one
structure variable to the other.
buuuu...@gmail. com wrote:
why array can't be assigned, like structs?
It probably because of the very close relationship between arrays and
pointers in C. Pointers can, and often do, point to arbitrarily sized
blocks of memory, which can't be assigned to one another by the
compiler.
In fact, in pre-ANSI C, even instances of structures could not be
automatically assigned to one another.
On Mar 8, 4:20 am, Flash Gordon <s...@flash-gordon.me.ukwro te:
buuuu...@gmail. com wrote, On 08/03/07 05:26:
why array can't be assigned, like structs?
Because the language does not allow it.
and
Because its the way language has been designed!
why? what's the reason? why array's cant be like any other type in C?
why it have to be different?
It probably because of the very close relationship between arrays and
pointers in C. Pointers can, and often do, point to arbitrarily sized
blocks of memory, which can't be assigned to one another by the
compiler.
why? why pointer and arrays have this relationship? There is no need!
And why only arrays are like this, and structs, integers, chars are
not
im asking this because i can't find any good reason for this behavior,
since array is just another type of the language
(sorry about my english)
On 8 Mar 2007 11:01:30 -0800, in comp.lang.c , bu******@gmail. com
wrote:
>On Mar 8, 4:20 am, Flash Gordon <s...@flash-gordon.me.ukwro te:
>buuuu...@gmail .com wrote, On 08/03/07 05:26:
why array can't be assigned, like structs?
Because the language does not allow it.
and
Because its the way language has been designed!
why? what's the reason? why array's cant be like any other type in C?
why it have to be different?
An array isn't a type. Its a derived type, and has different
behaviour. Similarly structs.
>im asking this because i can't find any good reason for this behavior,
since array is just another type of the language
Not in C.
--
Mark McIntyre
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan
santosh wrote:
buuuu...@gmail. com wrote:
>why array can't be assigned, like structs?
It probably because of the very close relationship between arrays and
pointers in C. Pointers can, and often do, point to arbitrarily sized
blocks of memory, which can't be assigned to one another by the
compiler.
In fact, in pre-ANSI C, even instances of structures could not be
automatically assigned to one another.
K&R1 was published in 1978. In that book BWK notes that DMR's compiler
implemented struct assignment. There was no Standard of course until
1989 and K&R1 does not describe it as part of C.
--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
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