xbasic for everyone Dr Wayne

[Thontlb]

Is there a resource re: errata and corrections to the code in the book?

[Peter.Wayne]

Good point. So far very few errors have been reported. On p. 21, I refer to "fname" in the text and "f_name" in the scripts. I don't believe any other substantial errors have been reported, but if you find them, let me know.

- Peter Wayne

[davej]

Would you prefer errors via this forum or private means?

Dave

[Peter.Wayne]

I'm happy to have them posted here; it will provide an ongoing resource for errata. Just a warning: Several of the "errors" that were reported to me, though, were not errors at all!

[davej]

Page 33: code segment at top of page referes to USB flash drive - explanatory paragraph referes to floppy diskette

page 43: top section(s) refer to chapter 13 - should be chapter 14

page 47: code segment for OnRowChange, line 4 "customer' misspelled

page 54: first paragraph, last line ...form in which... should read ..form on which...

page 60: second paragraph bnelow top code segment, line 3 - "When i is 4, i is" should read ... is 4, j is...

[Peter.Wayne]

Thanks, Dave. I have corrected those typos in the manuscript, should it ever be reprinted. But Terry wanted to know if there were errors and corrections to the code in the book, and so far no one has reported any errors in the actual scripts, just on occasion in the commentary. Anyone find any errors in the code?

[Bob Arbuthnot]

Peter,

Maybe it's something else I did, but I couldn't get the code on page 41 to work without deleting one of the = signs in front of "GODOT". After doing that the code worked as presented.

BA

[Peter.Wayne]

The "==" checks for EXACTLY EQUALS, which means that "godot" is not EXACTLY the same as "GODOT", and
"GODOT " is not EXACTLY the same as "GODOT". I don't the code is in error, you probably were not aware that it is a case-sensitive comparison.

[davej]

Peter,

on page 68, the code segment that reads:
cust=table.open("customer")
cust.index_open_put("customer_id")

generates an error because, on my system at least, there is no customer_id index - there is a customer_I index and a customer_O index, both of which have Order Expression of Customer_ID. When I changed customer_I to customer_Id, the code worked.

[Thontlb]

Object Oriented

Good point. So far very few errors have been reported. On p. 21, I refer to "fname" in the text and "f_name" in the scripts. I don't believe any other substantial errors have been reported, but if you find them, let me know.

- Peter Wayne

++++++++++++++++++++++++++++++++

Dr. Wayne,

I have worked through the global listOne code on page 303 several times without success.

Delcaraton:
'Date Created: 16-Jun-2006 06:58:47 PM
'Last Updated: 16-Jun-2006 07:05:18 PM
'Created By : Terry
'Updated By : Terry
define class global listone


dim entries as c
dim name as c





function size.get as n()
size.get=w_count(entries,crlf())
end function

function sort as v()
entries=sortsubstr(entries,crlf())
end function

function view as v()
ui_msg_box((name,entries+crlf()+"Number entries: "+self.size)
end function


function add as v(item as c)
entries=entries+item+crlf()
end function

function delete as v(item as c)
count=self.size
entry=wordat(items,entries,crlf())
If entry=1 then
entries=word(entry+1,crlf(),count-entry
else
entries=word(entries,1,crlf(),entry-1)+crlf()+\
word(entries,entry+1,crlf(),count-entry))

end if
end function
end class

This compiles fine.

In the interactive window the trouble begins whenn atempting to create a "listone"

mbrs=<<%srt%
#peter
#barry
#michael
#icha
#pam
#finian
#%str%
dim group as listone
Error 1

==================================

Am I missing something. I've checked the spelling several times. One thing I notice is that it is very common for A5 fo successfully compile script that wont run but that's a different issue.

Also this is the first I've ever seen of user class to inherit from in A5. I've created properties and methods for ms Access objects may times, however I not convinced of it's usefulness. There's very little documentation from microsoft and unless I missed something, the first with Alpha. Types and collections have been around, and I suppose an object is just a type with properties and methods.

In your professional opinion, is it worth the effort to create user obects?

Terry

P.S. Hopefully there aren't errors in your work. I'm notorious for having typos copying dode from a book to the screen. I realize that it could comprimise your work, but have you considered letting purhcasers of you book download the code files? It wouldn't rquire the text of the book, only the code and page reference. Then one can copy and paste after attempting it on their own to check for typos?

[davej]

Page 71, Xbasic for Everyone

Can anyone see why this code segment returns the error message indicated? I've gone over it any number of time, without success.

t=table.open("customer")
n=0
t.fetch_first()
while .not. t.fetch_eof()
n=iif(left(t.lastname,1)="M",n+1,n)
t.fetch_next()
end while
ERROR: Mismatched end of loop or if-block

Dave

[Peter.Wayne]

Terry,
You're right, you made a couple of typos. The code should be posted at the url indicated on page vii of the book; here is the fragment you need, in case it's not there:

define class global listone

dim entries as c
dim name as c

function size.get as n()
size.get=w_count(entries,crlf())
end function

function sort as v()
entries=sortsubstr(entries,crlf())
end function

function view as v()
ui_msg_box(name,entries+crlf()+"Number entries: "+self.size)
end function

function add as v(item as c)
entries=entries+item+crlf()
end function

function delete as v(item as c)
count=self.size
entry=wordat(items,entries,crlf())
If entry=1 then
entries=word(entry+1,crlf(),count-entry)
else
entries=word(entries,1,crlf(),entry-1)+crlf()+\
word(entries,entry+1,crlf(),count-entry)

end if
end function
end class

I don't know whether it pays to write user-defined classes. So far I haven't used any in real life programming, but that's not to say that I could not in the future. I haven't decided yet whether object-oriented programming is really an advance or not.

And Dave -- your problem is that you're trying to execute that script fragment in the interactive window. You can't just copy and paste into the interactive window. If you want to copy and paste code, put it into a new script window and then press the lightning bolt to run the code.

[JerryBrightbill]

Whwn I run this code, I get the expected result in Alpha Sports - 9 records

dim t as p
dim n as n
t=table.open("customer")
n=0
t.fetch_first()
while .not. t.fetch_eof()
	n=if(left(t.lastname,1)="M",n+1,n)
	t.fetch_next()
end while
 
t.close()
ui_msg_box("",str(n))

However, it is slightly more efficient to only set the value of 'n' on a match

dim t as p
dim n as n
t=table.open("customer")
n=0
t.fetch_first()
while .not. t.fetch_eof()
	if left(t.Lastname,1) = "M"
		n= n + 1
	end if 
	t.fetch_next()
end while
t.close()

Neither of these methods actually are very efficient for any large tables and a query is a better bet and many times faster

query.filter = "left(lastname,1) = 'M'"
query.order = "lastname"
t = table.open("tblcontacts")
qdx = t.query_create()
n = qdx.records_get()
t.close()

On a 10,000 record file, the first method took about 1.64 secords to find 1000 records, the second method took about 1.48, but the query ran in .015

[davej]

Jerry,

Thanks. I'm not concerned about speed at the moment - I made my mind up to get a handle on Xbasic, so right now I'm working my way through Peter's book trying to build some comfort level. Speed will come in play in the near future.

Dave

[urbanski]

On page 280 of the calendar application I get a 500 server error unexpected value in this line.
ownerlist=table.external_record_content_get("[PathAlias.adb_path]\calendar_owner",\ "owner","owner","active=.t."
I just don't see what the error is in this line.

Jim