How many Nested (IF's) are allowed

[Chuck Bytes]

Anyone know if there is a limit to the number of nested (IF) statements allowed in a single function command.

I know Excel 2003 has a limit to 7 nested (IF) statements, that includes the .F. result, just wondering if Alpha has such a limit.

if(class=4, "Senior", if(class=3, "Junior", if(class=2, "Sophomore", "Freshman")))............)))))))))) ?

[Steve Workings]

Re: How many Nested (IF's) are allowed

You might consider using the Case() function. It's simpler.

Edit: anticipating someone pointing out the documentation states or at least suggests a limit of 16 Case statements, this shows otherwise:

case(.f.,"a",.f.,"b",.f.,"c",.f.,"d",.f.,"e",.f.,"f",.f.,"g",.f.,"h",.f.,"i",.f.,"j",.f.,"k",.f.,"l",.f.,"m",.f.,"n",.f.,"o",.f.,"p",.f.,"q",.f.,"r",.f.,"s",.f.,"t",.f.,"u",.f.,"v",.f.,"w",.f.,"x",.f.,"y",.t.,"z")

[csda1]

Re: How many Nested (IF's) are allowed

Anyone know if there is a limit to the number of nested (IF) statements allowed in a single function command.

I know Excel 2003 has a limit to 7 nested (IF) statements, that includes the .F. result, just wondering if Alpha has such a limit.

if(class=4, "Senior", if(class=3, "Junior", if(class=2, "Sophomore", "Freshman")))............)))))))))) ?

As far as I know, Alpha has no practical limit, as I believe it just uses available stack space for memory. The case statement may have a limit, only because it uses one function, rather than stacking the usages, however, I bet it's beyond most to exceed.

Expression length in database fields (*.dbf) will be limited to 255 characters, and may be limited to 1024 in many places. XBasic expressions, have no real length limitation.

[Mike Wilson]

Re: How many Nested (IF's) are allowed

XBasic expressions, have no real length limitation.

So what is this that the documentation on specifications is relating (attached)?

[MikeC]

Re: How many Nested (IF's) are allowed

Mike,
The expression builder may have a limit but by using variables or UDFs in the expression builder the limit does not really affect the amount of characters you can use as a variable/UDF is basically unlimited for length I understand.....good thing too as otherwise I couldn't use the huge filter lists that I need for various projects!!

[csda1]

Re: How many Nested (IF's) are allowed

Hi Mike,

So what is this that the documentation on specifications is relating (attached)?

This is related to places in Alpha Five (e.g. fieldrule expressions) that have a limit for the expression (1024). Some of the limits you may find are

• Expression and filters for Index definitions have a limit as well due to the DBF format, something like 212 characters for the index expression, probably 512 for the filter, although the input may allow more than that in text.
• Action script definitions (which are just code generators for XBasic and Xdalog) will allow whatever they have been designed to allow
• Inline XBasic for Action Scripts may have a maximum length of 16 lines, but that may have been changed, although there is no inherent limitation in any XDialog or Ation Script.
• XDialog and maybe someplaces in XBasic that use other Active X controls (e.g. Listview objects), they may have limits placed on it by the Active X control.
• Calculated fields on layouts have a limit of 1024 characters, and there may be similar limits on expressions used elsewhere in a layout's definitions
• Character and Blob variables have no limits in length to their contents, and the size of their contents does not affect the size of an expression they are used in (unless you are embedding their contents into the expression, typically as a constant)
• The code editor has a limit of about 13000 lines for any single piece of code, but that might be a length limitation in bytes, thus there is no practical limit on expressions used in code.
• The data dictionaries themselves have a file maximum size of 2 Gigabytes for any file.

Mike C,

Mike,
The expression builder may have a limit but by using variables or UDFs in the expression builder the limit does not really affect the amount of characters you can use as a variable/UDF is basically unlimited for length I understand.....good thing too as otherwise I couldn't use the huge filter lists that I need for various projects!!

When you use a UDF (or actually any "slower" function, UDF or built-in) in an index's filter or order expression, it pays a real penalty in speed. This is only really seen when rebuilding an index or creating a query. I'd use it as a last resort if you don't have space in the expression. Large variables don't slow things down except as in which each variable is operated on by UDF's or built-in function.

[MikeC]

Re: How many Nested (IF's) are allowed

Ira,
I normally use variables for long filters, but someone once suggested using a function for my purpose....and it did work, but used a variable so I lucked out and chose correctly! I never realized how much I would have to use speed recommendations (mostly yours) in my work but it is a constant battle to keep my projects running fast enough to be user friendly now.

Thanks again Ira.

[csda1]

Re: How many Nested (IF's) are allowed

Hi Mike,

Ira,
I normally use variables for long filters, but someone once suggested using a function for my purpose....and it did work, but used a variable so I lucked out and chose correctly! I never realized how much I would have to use speed recommendations (mostly yours) in my work but it is a constant battle to keep my projects running fast enough to be user friendly now.

Thanks again Ira.

You're welcome.

My number 1 guide is that data will grow to such a point as to make any code's speed unusable! So I always code for speed by choosing algorithms & methods to process, and then tailor which A5 functions/methods I use to be the "right" ones.

I'm amazed that Google is capable of indexing the Internet without it taking hours to process! (of the estimated 5 billion terabytes on the internet)

[Chuck Bytes]

Re: How many Nested (IF's) are allowed

Well, I tested the limits of the IF statement with 37 incidences and it worked without a flaw.

Excellent.

I know this is not the most efficient function to use, but for a novice, the IF statement is a life saver until something better is figured out.

A5 keeps impressing me. Probably because I am a novice and can put out an application that would rival the competitions that cost thousands upon thousands.

Well done fellas.