Enum vs Char * array

[Travis]

Just curious, which takes less memory?

enum Months {
JAN, FEB, MAR,
APR, MAY, JUN,
JUL, AUG, SEP,
OCT, NOV, DEC
};

static const char *Months[12] =
{
"JAN", "FEB", "MAR",
"APR, "MAY", "JUN",
"JUL", "AUG", "SEP",
"OCT", "NOV", "DEC"
};

[Virtual_X]

On Jul 12, 4:06 pm, Travis <travis.bow...@ gmail.comwrote:

Just curious, which takes less memory?

static const char *Months[12] =
{
"JAN", "FEB", "MAR",
"APR, "MAY", "JUN",
"JUL", "AUG", "SEP",
"OCT", "NOV", "DEC"};

this method is invalid because of two reasons
1- char *Months[12] is refer to an array of pointers which consist of
12 pointer
2- if we make it as char so cannot assign data like that
"JAN","FEB",... ..
you need only single character such as 'a','b'
but if you need to make some thing like that you can use the type
string

ie:
#include <string>

main()
{
string Months[12] = {"JAN","FED",.. ....}
}

and for the memory use , i think the enum is less than string in
memory usage because it's refer to numbers not strings

finally if you need to more save to the memory you can use

bool x[12]={1,2,3,.....};

which 1 refer to JAN and 2 refer to FEB ....

because bool is use only 1 byte unlike string or enum

[Default User]

Virtual_X wrote:

On Jul 12, 4:06 pm, Travis <travis.bow...@ gmail.comwrote:

Just curious, which takes less memory?

static const char *Months[12] =
{
"JAN", "FEB", "MAR",
"APR, "MAY", "JUN",
"JUL", "AUG", "SEP",
"OCT", "NOV", "DEC"};

this method is invalid because of two reasons
1- char *Months[12] is refer to an array of pointers which consist of
12 pointer
2- if we make it as char so cannot assign data like that
"JAN","FEB",... ..
you need only single character such as 'a','b'

What are you talking about? The code shown creates an array of 12
pointer to constant char, which are intialized with pointers to various
string literals. Perfectly valid, other than the OP left off one of the
" around APR.


Brian

[Default User]

Travis wrote:

Just curious, which takes less memory?

enum Months {
JAN, FEB, MAR,
APR, MAY, JUN,
JUL, AUG, SEP,
OCT, NOV, DEC
};

static const char *Months[12] =
{
"JAN", "FEB", "MAR",
"APR, "MAY", "JUN",
"JUL", "AUG", "SEP",
"OCT", "NOV", "DEC"
};

Implementation-specific. Probably the enum.

However, the two constructs are so different that a size comparison is
fairly useless.

Brian

[Travis]

On Jul 12, 4:51 pm, "Default User" <defaultuse...@ yahoo.comwrote:

Virtual_X wrote:

On Jul 12, 4:06 pm, Travis <travis.bow...@ gmail.comwrote:

Just curious, which takes less memory?

static const char *Months[12] =
{
"JAN", "FEB", "MAR",
"APR, "MAY", "JUN",
"JUL", "AUG", "SEP",
"OCT", "NOV", "DEC"};

this method is invalid because of two reasons
1- char *Months[12] is refer to an array of pointers which consist of
12 pointer
2- if we make it as char so cannot assign data like that
"JAN","FEB",... ..
you need only single character such as 'a','b'

What are you talking about? The code shown creates an array of 12
pointer to constant char, which are intialized with pointers to various
string literals. Perfectly valid, other than the OP left off one of the
" around APR.

Brian

Thank you. I didn't know what that person was talking about either.
Sorry I forgot a " near April. That's what you get for so much rain
April!

I was just curious, because some of the older guys I work with do the
char * thing and I like the clean look of ENUM but if we're talking
performance hit (we are in an OS dept), then maybe I change my ways.

[James Kanze]

On Jul 13, 1:56 am, Travis <travis.bow...@ gmail.comwrote:

I was just curious, because some of the older guys I work with
do the char * thing and I like the clean look of ENUM but if
we're talking performance hit (we are in an OS dept), then
maybe I change my ways.

As Alf said, they don't do anywhere near the same thing. In
particular, if you use the enum:

Months m = JAN ;
std::cout << m ;

isn't going to display anything useful. On the other, you can't
even write something like the above with the array of char
const*.

If all you're concerned about is storing the values, it will
depend on the machine and the compiler. In one case, you're
storing an enum value, in the other, a pointer. On many
machines, they have the same size. (On the other hand, it's
possible to use bit fields with the enum type, but not with the
pointer.)

In sum, both have their place. (I actually have a program
which, given the enum, will generate a table with the strings,
and mapping functions each way. I often need string
representations of enum values.)

--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]

[Jim Langston]

"Travis" <tr***********@ gmail.comwrote in message
news:11******** **************@ n60g2000hse.goo glegroups.com.. .

On Jul 12, 4:51 pm, "Default User" <defaultuse...@ yahoo.comwrote:

>Virtual_X wrote:

On Jul 12, 4:06 pm, Travis <travis.bow...@ gmail.comwrote:
Just curious, which takes less memory?

static const char *Months[12] =
{
"JAN", "FEB", "MAR",
"APR, "MAY", "JUN",
"JUL", "AUG", "SEP",
"OCT", "NOV", "DEC"};

this method is invalid because of two reasons
1- char *Months[12] is refer to an array of pointers which consist of
12 pointer
2- if we make it as char so cannot assign data like that
"JAN","FEB",... ..
you need only single character such as 'a','b'

What are you talking about? The code shown creates an array of 12
pointer to constant char, which are intialized with pointers to various
string literals. Perfectly valid, other than the OP left off one of the
" around APR.

Brian

Thank you. I didn't know what that person was talking about either.
Sorry I forgot a " near April. That's what you get for so much rain
April!

I was just curious, because some of the older guys I work with do the
char * thing and I like the clean look of ENUM but if we're talking
performance hit (we are in an OS dept), then maybe I change my ways.

It depends on how you are planning on using the months. Enumerators on my
system are stored in 4 bytes. A char pointer on my system also takes up 4
bytes. I can cast from and to enums from ints sometimes with difficulty.

Now, the problem comes in when you have some information stored in a tabke,
such as "JAN". How do you determine that that's the enum JAN? There is no
text string "JAN" in the program unless you define it elsewhere. However,
it is possible to store it as an int value, such as "0" and read it, then
cast to an enum.

I tend to use enums myself, especially when there is no user input on the
value. I store them as integers, read them as integers then cast them to
the enum.

Can enums be faster? Well, yes, it's fairly quick for the computer to
figure out if 1 == 1. Takes longer to determine if "JAN" == "JAN".

As to weather this is your bottle neck or not is very hard to say without
seeing code.

I would say, however, that without trying to determine if "JAN" == JAN (text
== enum) an enum generally will be faster. If you have to convert from text
to an enum, an enum will be slower, and more bug prone.

[Marcus Kwok]

James Kanze <ja*********@gm ail.comwrote:

(I actually have a program
which, given the enum, will generate a table with the strings,
and mapping functions each way. I often need string
representations of enum values.)

For those curious on how to do this, here is a page that gives a few
approaches:

http://www.comeaucomputing.com/techtalk/#enumtostring

--
Marcus Kwok
Replace 'invalid' with 'net' to reply