Something for the weekend #6: VFP functions 2

Mike Lewis · Mar 13, 2015

An easy one this time. I expect we'll see some good replies before the end of Friday.

Can you think of any built-in VFP function that is always guaranteed to return exactly the same result every time you use it?

Just to be clear, the function will either take no parameters; or, if it takes one or more parameters, it will return the same result regardless of what parameters you pass.

Off-hand, I can think of one possible contender, although I'm not completely sure of it.

Before you post a reply, please see my note below re spoilers.

Mike

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Mike Lewis (Edinburgh, Scotland)

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Mike Lewis · Mar 13, 2015

Note re spoilers

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Mike

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Mike Lewis (Edinburgh, Scotland)

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Tore Bleken · Mar 13, 2015

PI().

EzLogic · Mar 13, 2015

Well, same result everytime on MY machine?
if so,

?os()

if same everytime on ANY Machine?

?pi()

Ez Logic
Michigan

Mike Lewis · Mar 13, 2015

Well, same result everytime on MY machine?

No, sorry - not allowed. It has to always be the same - regardless of the computer, VFP version, Windows version, day of the week, whatever.

The other suggestions are what I had in mind. But consider this:

[tt]SET DECIMALS TO 2
x2 = PI()
SET DECIMALS TO 4
x4 = PI()
? x2 && 3.14
? x4 && 3.1416[/tt]

Any comments on that?

Mike

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Mike Lewis (Edinburgh, Scotland)

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Tore Bleken · Mar 13, 2015

Set Decimals" changes the value you see displayed on the screen, not the actual value.

Olaf Doschke · Mar 13, 2015

There are many of those, aren't there?

? MEMORY() && since foxpro became "Visual" always returns 640 - You will get different results for MEMORY

though.
? ALANGUAGE(laLang) && aside of the name of the resulting array, the value will always be the same, as the language doesn't change. It will differ in different VFP versions though.

http://www.tek-tips.com/viewthread.cfm?qid=1746336

If you take SYS

with a specific n as one function, there are several SYS() functions returning a constant result. If you see it as one function, the result obviously varies with the main first parameter.
Of course on of these syss functions is
? SYS(12) && as mentioned in MEMORY()
? SYS(9) && serial number, will differ in different versions, of course. This is also displayed in the "About Microsoft Visual FoxPro" dialog.
...

Bye, Olaf.

Olaf Doschke · Mar 13, 2015

I didn't write that link in there.

Not the first time it happens, it links to this same thread.

I was wrong on at least one function mentioned. And I see which function I forgot now. Shame on me. Didn't thought about it.

Bye, Olaf.

Mike Lewis · Mar 13, 2015

"Set Decimals" changes the value you see displayed on the screen, not the actual value.

That's right. So, how do you explain the code I posted? The last two lines appear to show different results, even though DECIMALS is set to 4 for both of them.

Mike

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Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

Mike Lewis · Mar 13, 2015

Olaf,

Your first suggestion is good. As far as I can see, it meets the requirements.

However, I'm less happy with your other suggestions, because they will return different values in different environments (VFP version, etc).

SYS

for a given n is OK, if it always returns the same value, but the only one I can think of is the one you quoted. Do you know any others.

In order to widen the discussion, I'm prepared to accept any functions that return a different value in FPD or FPW (or even Foxbase), provided the returned value is constant in Visual Foxpro.

Mike

__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

Olaf Doschke · Mar 13, 2015

Consider this:

SET DECIMALS TO 2
x2 = PI()
SET DECIMALS TO 4
x4 = PI()
? x2 && 3.14
? x4 && 3.1416
? 100*x2 && 314.16, so the other digits are still stored in x2. Numeric variables have a precision stored with them.

Bye, Olaf.

Mike Lewis · Mar 13, 2015

Olaf,

You are completely correct (although I'm not sure I understand why):

[tt]? x2 && 3.14
? x4 && 3.1416
? x2 = x4 && .T.
[/tt]

Mike

__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

Dan Freeman · Mar 13, 2015

IsColor()
(Unless you have a video card older than VGA.)

Mike Lewis · Mar 13, 2015

Nice one, Dan.

Mike

__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

vgulielmus · Mar 13, 2015

RAISEEVENT()

Respectfully,
Vilhelm-Ion Praisach
Resita, Romania

Mike Lewis · Mar 13, 2015

Excellent, Wilhelm. I didn't think of that.

Mike

__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

Mike Lewis · Mar 13, 2015

Earlier, Olaf mentioned that some SYS() functions would qualify - assuming you accept that the first parameter makes it a unique function (in other words, SYS(1) is a different function than SYS(2), and so on).

I've just been looking through the list of SYS() functions, and I see that a lot of them always return an empty string. These are essentially functions that perform some task; the returned value is irrelevant. Examples include SYS(1500) - Activate a System Menu Item; SYS(1023) - Disable Help Diagnostic Mode; and SYS(3056) - Read Registry Settings.

I also spotted:

- SYS(13) - Printer Status - "For versions of Visual FoxPro running on Windows, SYS(13) always returns READY." (Is it safe to assume that Visual Foxpro will always run under Windows?)

- SYS(2006) - Current Graphics Card - "Returns the type of graphics card and monitor you are using." On my system, the returned value is "Color/Color". Can we assume that would always be the same? (Dan suggested something similar.)

Anyway, I hope some of you find this sort of thing interesting. I certainly do.

Mike

__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

TamarGranor · Mar 13, 2015

Here are a few:

SYS(23)
SYS(24)
SYS(13)
PRINTSTATUS()

I can probably dig up some more, but I'll leave some fun for others.

Tamar

Olaf Doschke · Mar 13, 2015

See here, Mike:

https://msdn.microsoft.com/en-us/library/e9261kx6(v=vs.80).aspx

ev_width stores a display width, the number itself is stored in ev_real, and that part of the c structure is equal, no matter how you SET DECIMALS.

Bye, Olaf.

Olaf Doschke · Mar 13, 2015

Some system variables are also constant since a very long time, eg _Mac and _Windows.

Bye, Olaf.

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