RAN Function

[alexmuir]

Hello

As I see it the singular and primary objective of the RAN function is to generate a unique random number.

What I have found is that it sometimes duplicates numbers.

Has anyone else experienced this?

Thanks for your help. It is very much appreciated.

Kind regards

Alex

[Stan Mathews]

Re: RAN Function

Not sure what a unique random number might be. The rand() function does have this note.

RAND() always generates the same sequence of numbers. You can get an unpredictable series by looping through the RAND() function loops times before starting to use its output. The following routine uses the current time to define loops.

loops = val( right( str( int( toseconds( time() ) ) ),3) )
? loops
= 507
for i = 1 to loops
    rand()
next
? rand()
= 0.338623046875

[metadyne]

Re: RAN Function

Not sure what a unique random number might be. The rand() function does have this note.

loops = val( right( str( int( toseconds( time() ) ) ),3) )
? loops
= 507
for i = 1 to loops
    rand()
next
? rand()
= 0.338623046875

I tried the rand function to generate a unique number for each record in a child table on a networked application in order to open a form based on the current line no. Auto-increment is not recommended on networks. I thought that rand * 100000000 would give a unique number each time but have now found otherwise.

A random number generator should always give a unique number each time it is run (assuming a big enough number is generated).

I am now using date and time with seconds to 2dp to get a unique line no instead.

[Stan Mathews]

Re: RAN Function

A random number generator should always give a unique number each time it is run

If it did that it wouldn't be random. It would have to include some algorithm to avoid repetition making it not truly random.

[martinwcole]

Re: RAN Function

What your doing is most likely unnecessary
when you start your app dim a global variable called rnum,n (numeric)

In the embedded browse in the onrowdoubleclick event put
t=table.current() 'or t=table.get("thenameofthechildtable")
rnum=t.recno()
then
form.view("the name of your form")
or
if you want to open the form as a smaller dialog window
f=form.view("the name of your form","dialog")
f.close()

on the form that you are going to open, open the form in design mode and set the filter for the form to recno()=var->rnum

[Ted Giles]

Re: RAN Function

Throwing a dice and getting 3 sixes in a row is still random.
Tossing a coin and getting 3 heads in a row is random.
Uniqueness is not the same as randomness.

[DaveM]

Re: RAN Function

Auto-increment is not recommended on networks.

Who said that? I have used them since I started with networked apps.

[Allen Klimeck]

Re: RAN Function

You should look at:

API_UUIDCREATE()

[metadyne]

Re: RAN Function

Using the recno() function would lead to problems because every day my networked apps are compacted and re-indexed so what is record 1234 today would like be a totally different number tomorrow and another record might become 1234 instead.

[martinwcole]

Re: RAN Function

wrong - it is using the current record number - it will always be correct.

[Ted Giles]

Re: RAN Function

Until it gets packed and there are deleted records in there.
Then the word of pain kicks in.

[martinwcole]

Re: RAN Function

wrong again - when you get the record number of a specific record, it is always the current record number - regardless of deleted records

[martinwcole]

Re: RAN Function

the current record number is dynamic, not static
t=table.current()
dim global rnum as n
rnum=t.recno() - this is the record number as of this second

[Ted Giles]

Re: RAN Function

So how would you use a dynamic value as a persisted value?

[martinwcole]

Re: RAN Function

you are not using a "persisted" record number - you are not "storing" it
if the code below you are getting the current record number as of this second, and then opening a form filtered the the recno()=var->rnum

have been using this approach for maybe 15 years - first got the idea from Dr. Peter Wayne.
Alpha also uses that approach when you "zoom" to a record on another form

the current record number is dynamic, not static
t=table.current()
dim global rnum as n
rnum=t.recno() - this is the record number as of this second