1. a few questions
Can someone explain 'short circuit' to me (or give me an example). I find no
reference to it in the manual..
In EU data base I see no way to perform a 'read next' or 'read previous'
type function. I would like to be able to do this and get the data elements
out in sorted (by key) order. Is this do'able? The are apparently stored in
sorted order since a binary search is done with a db_find.
Can someone explain the search path. It seems to open files and data bases
that the entire path has to be specified.
2. Re: a few questions
----- Original Message -----
From: George Walters <gwalters at sc.rr.com>
Subject: a few questions
>
> Can someone explain 'short circuit' to me (or give me an example). I find
no
> reference to it in the manual..
Suppose you have the code:
if a = 1 and foo(bar) = 3 then
do something
Supposing a did not equal 1,
then Euphoria would not bother to look at foo(), so foo() would not be
executed.
Sometimes you might be expecting foo() to do some work besides just
returning
a value to compare, and in this case, that work wouldn't get done.
Hence the warning.
Regards,
Irv
3. Re: a few questions
> In EU data base I see no way to perform a 'read next' or 'read previous'
> type function. I would like to be able to do this and get the data
elements
> out in sorted (by key) order. Is this do'able? The are apparently stored
in
> sorted order since a binary search is done with a db_find.
The keys are stored in sorted order with the base.
To read them all, loop from 1 ... db_table_size()
To select the prev or next record, either keep a counter,
or, if you have done a lookup, and want the previous or next
record from that point:
x = db_find_key(IHaveThisKey)
if x > 0 then -- key was found, so
prevkey = db_record_key(x-1)
nextkey = db_record_key(x+1)
nextdata = db_record_data(x+1)...
You may want to put some sanity checks on x before you try to retrieve
record numbers
less than 1 or higher than the size of the table.
Regards,
Irv
4. Re: a few questions
Irv, If I have a particular key 'abc' and it's record and I want the next
record (in sorted order) it will not necessarily be db_record_key(x+1) , the
next record's key. The records are not in sorted order, so the next record's
key will not be the next (sorted) key.
Am I understanding this correctly? And if you want to start at the
beginning, you don't have a key. Do you use a key of "" to position to the
beginning of the file?
..george
----- Original Message -----
From: "Irv Mullins" <irvm at ellijay.com>
To: "EUforum" <EUforum at topica.com>
Subject: Re: a few questions
>
> > In EU data base I see no way to perform a 'read next' or 'read previous'
> > type function. I would like to be able to do this and get the data
> elements
> > out in sorted (by key) order. Is this do'able? The are apparently stored
> in
> > sorted order since a binary search is done with a db_find.
>
> The keys are stored in sorted order with the base.
> To read them all, loop from 1 ... db_table_size()
> To select the prev or next record, either keep a counter,
> or, if you have done a lookup, and want the previous or next
> record from that point:
> x = db_find_key(IHaveThisKey)
> if x > 0 then -- key was found, so
> prevkey = db_record_key(x-1)
> nextkey = db_record_key(x+1)
> nextdata = db_record_data(x+1)...
>
> You may want to put some sanity checks on x before you try to retrieve
> record numbers
> less than 1 or higher than the size of the table.
>
> Regards,
> Irv
>
>
>
>
>
5. Re: a few questions
On Monday 30 July 2001 09:22, George Walters wrote:
>
> Irv, If I have a particular key 'abc' and it's record and I want the next
> record (in sorted order) it will not necessarily be db_record_key(x+1) ,
> the next record's key. The records are not in sorted order, so the next
> record's key will not be the next (sorted) key.
> Am I understanding this correctly? And if you want to start at the
> beginning, you don't have a key. Do you use a key of "" to position to the
> beginning of the file?
No. The record keys are always stored sorted.
If you put in a random list of names:
Zorro
Bubba
Norton
Chuck
Al
Then they will be stored in the database as:
1. Al
2.. Bubba
3. Chuck
4. Norton
5. Zorro
Therefore, to start at the beginning of the list, retrieve record 1,
For the list above, db_record_key(1) would return Al
db_record_key(db_table_size()) would return Zorro.
Regards,
Irv
6. Re: a few questions
I understand now... I think the doc is misleading... it says "Return the key
portion of record number i in the current table" and the key of record x+1
is not the same as key(x+1).. It should probably say "Return the i'th key in
the current table".
thanks...
..george
----- Original Message -----
From: "Irv Mullins" <irvm at ellijay.com>
To: "EUforum" <EUforum at topica.com>
Subject: Re: a few questions
>
> On Monday 30 July 2001 09:22, George Walters wrote:
> >
> > Irv, If I have a particular key 'abc' and it's record and I want the
next
> > record (in sorted order) it will not necessarily be db_record_key(x+1) ,
> > the next record's key. The records are not in sorted order, so the next
> > record's key will not be the next (sorted) key.
> > Am I understanding this correctly? And if you want to start at the
> > beginning, you don't have a key. Do you use a key of "" to position to
the
> > beginning of the file?
>
> No. The record keys are always stored sorted.
> If you put in a random list of names:
> Zorro
> Bubba
> Norton
> Chuck
> Al
>
> Then they will be stored in the database as:
> 1. Al
> 2.. Bubba
> 3. Chuck
> 4. Norton
> 5. Zorro
>
> Therefore, to start at the beginning of the list, retrieve record 1,
> For the list above, db_record_key(1) would return Al
> db_record_key(db_table_size()) would return Zorro.
>
> Regards,
> Irv
>
>
>
>
>
