What I would like to do:
I would like to use operator overloading in Excel to run custom functions on my custom data types. For example, when evaluating a formula, I want Excel to run my function instead of the '+' operator when the calculation involves one of my custom data types.
Why I want to do it:
In analytical chemistry, every number has an uncertainty attached to it and is written:
13.56 (±0.02) mm
I would like to create a custom data type that keeps the magnitude and the uncertainty of the number together in the same cell.
Additionally, I want to implement operator overloading, so when I write
=A1+A2
and either A1 or A2 contains an uncertainty-type number, my custom function runs instead of the default
'+' operator to calculate the uncertainty.
This would make my spreadsheets much cleaner, as currently, I have to write such a statement as
=ADD_UNC(A1, A2)
Which is fine for very simple equations, but becomes a pain when the operation I am trying to form is even slightly non-trivial.
=MULT_UNC(A3, ADD_UNC(MULT_UNC(A5, A1, A2), A3)
vs.
=A3*((A1*A2)+A3)
Why I assume this is possible:
I know in real, full-blown programming languages such as C#, operator overloading is very common and very easy to perform.
Thank you for your help,
Michael
Not possible in VBA. VBA was intended to provide scripts which help with automation. You see, we call them macro. VBA is not built on top of modular classes or objects. Your VBE writes direct P-code the moment you type/ hit enter in the editor. VBA is awesome and packs alot of features but expecting these kind of facilities in VBA is a bit of stretch. No possibility to have this feature even in future. and Just a suggestion, never worry too much about code-cosmetics, they are useless overhead.
Here is a hack using the Worksheet_Change event. You can essentially place in a cell that contains a "+" character anything you want, thereby effectively disengaging the "+" signs normal function.
Private Sub Worksheet_Change(ByVal Target As Range)
If UBound(Split(CStr(Target), "+")) > 0 Then
Target = "Overloaded"
Else:
Target = "Not overloaded"
End If
End Sub
Related
Ever since I learnt that Excel is now Turing-complete, I understood that I can now "program" Excel using exclusively formulas, therefore excluding any use of VBA whatsoever.
I do not know if my conclusion is right or wrong. In reality, I do not mind.
However, to my satisfaction, I have been able to "program" the two most basic structures of program flow inside formulas: 1- branching the control flow (using an IF function has no secrets in excel) and 2- loops (FOR, WHILE, UNTIL loops).
Let me explain a little more in detail my findings. (Remark: because I am using a Spanish version of Excel 365, the field separator in formulas is the semicolon (";") instead of the comma (",").
A- Acumulator in a FOR loop
B- Factorial (using product)
C- WHILE loop
D-UNTIL loop
E- The notion of INTERNAL/EXTERNAL SCOPE
And now, the time of my question has arrived:
I want to use a formula that is really an array of formulas
I want to use an accumulator for the first number in the "tuple" whereas I want a factorial for the second number in the tuple. And all this using a single excel formula. I think I am not very far away from succeeding.
The REDUCE function accepts a LET function that contains 2 LAMBDAS instead of a single LAMBDA function. Until here, everything is perfect. However, the LET function seems to return only a "single" function instead of a tuple of functions
I can return (in the picture) function "x" or function "y" but not the tuple (x,y).
I have tried to use HSTACK(x,y), but it does not seem to work.
I am aware that this is a complex question, but I've done my best to make myself understood.
Can anybody give me any clues as to how I could solve my problem?
Very nice question.
I noticed that in your attempts you have given REDUCE() a single constant value in the 1st parameter. Funny enough, the documentation nowhere states you can't give values in array-format. Hence you could use the 1st parameter to give all the constants in (your case; horizontal) array-format, and while you loop through the array of the 2nd parameter you can apply the different types of logic using CHOOSE():
=REDUCE({0,1},SEQUENCE(5),LAMBDA(a,b,CHOOSE({1,2},a+b,a*b)))
This way you have a single REDUCE() function which internal processes will update the given constants from the 1st parameter in array-form. You can now start stacking multiple functions horizontally and input an array of constants, for example:
=REDUCE({0,1,100},SEQUENCE(5),LAMBDA(a,b,CHOOSE({1,2,3},a+b,a*b,a/b)))
I suppose you'd have to use {0\1} and {1\2} like I'd have to in my Dutch version of Excel.
Given your accumulator:
Formula in A1:
=REDUCE(F1:G1,SEQUENCE(F3),LAMBDA(a,b,CHOOSE({1,2},a+b,a*b)))
So I quite often find myself doing tasks on Excel which involve evaluating a text string as an array. Generally speaking I just use this:
Function EVAL(Ref As String)
EVAL = Evaluate(Ref)
End Function
So the formula will be, for example:
=EVAL("{"&CHAR(34)&SUBSTITUTE(TEXTJOIN(";",TRUE,MID(Index[Industries],2,LEN(Index[Industries])-2)),";",CHAR(34)&";"&CHAR(34))&CHAR(34)&"}")
The cells in this example will have contents like:
;Automotive;Rail;Energy;
;Automotive;Rail;
;Energy;
;Automotive;Aerospace;
(As it happens this is the precise problem I'm stuck on right now, though it has come up in different ways in the past.)
This has worked for me in the past, but I've been running into difficulties lately.
I have come to the conclusion it isn't working because application.evaluate, it turns out, has a character limit of 255. I've seen examples of VBA tricks to bypass this for text strings that are formulas rather than arrays, but copy-pasting those they don't seem to work for when I'm using it to interpret a text string as an array rather than as a formula.
Is there some trick to get this to work? (Or, indeed, is there some alternative method to achieve this altogether?)
Right, as per my comments, if you are using ms365, you could avoid your workbook to be xlsm just because you need to split values into an array. Make use of what is available with native functions, for example:
Formula in C2:
=TEXTSPLIT(CONCAT(A1:A4),,";",1)
Formula in D2:
=FILTERXML("<t><s>"&SUBSTITUTE(CONCAT(A1:A4),";","</s><s>")&"</s></t>","//s[node()]")
Note 1: As per time of writing you'd need to enable the BETA-channel to gain access to TEXTSPLIT(), and if I recall correctly your version (2203) is allowed to start using this function. Just google how to get access and update your Excel.
Both options can obviously be nested inside the UNIQUE() function.
Note 2: If at any point CONCAT()'s limits are reached (32767 characters, thanks #ScottCraner), maybe you can avoid using that with help of the lambda's helper function REDUCE():
=TEXTSPLIT(REDUCE("",A1:A4,LAMBDA(a,b,a&b)),,";",1)
Note 3: In case you can't update your Excel just yet, and you wonder how to use FILTERXML(), don't mind me refering you to another post I wrote a while back here.
I've been using a rather long embedded CUBEVALUE() function, which is a pain to work with. It looks something like:
=IFERROR(VALUE(CUBEVALUE(arg1;arg2;arg3));CUBEVALUE(arg1;arg2;arg3))
Due to the CUBEVALUE function and its arguments, it's becoming a REALLY long function and thus not easy to work with. Since there are only 3 arguments, which are written in different cells, I'd like to create something like
=MyFunction(A1,A2,A3)
and use A1, A2 and A3 as "arg1, arg2, arg3" in the function mentioned first. This way its possible to "pull" the function so it would calculate using the input in B1:B3 and C1:C3 etc. as well.
The function works fine and can be pulled through and such, but my question is how to rename this loooong function into something more user-friendly, as it requires only 3 cells as an input and the rest of the text in the function just makes it hard to use for end-users.
Using UDF is not an option because CUBEVALUE can't be called through VBA... and any attempt to stich strings together and using the final result with INDIRECT also seems to fail..
In a similar question on this site, someone refers to using "asynchronous UDF's", but no further information was given (and what I could find seemed irrelevant).
You shouldn't really have several long cube functions. Allocate some space in hidden rows/columns or in header rows/columns to add your cubemember functions. Then throughout most of your report, you should just have cubevalue functions that reference other cells with error handling around them. Proper use of absolute and relative references are your friend.
Peter Meyers has some great tips for this here, slides 20 - 24. I have an example Excel file with cube functions on my blog here.
If I type the formula 1/4*pi()*($A$1)^2 as a string in a cell and assuming I have a value in $A$1, I use the following VBA function in a third cell to evaluate the formula:
Public Function E(byval TextFormula as String) as Variant
E = Evaluate(TextFormula)
End Function
Is there a way to use math characters like •, √, ¼, π, ², etc. so that my typed-out formula looks more agreeable? Even translate '[' and ']' as '(' and ')'. I can just iterate through an array replacements using REPLACE() function for the simple characters but what about the extended characters like π?
For the really sharp macro'ers...
What about showing intermediate steps (iterations) as in (2*3) + (2.5*4) evaluates to 6 + 10 in the first iteration and then 16 in the next iteration. Asside: I would want the iterations to stop just before each set of addings/subtractings because I sometimes like to know what the relative magnitudes of the individual evaluated terms are to see what part of my formula is controlling the result.
And for the mega-genius ones...
What about mixed units? Such as typing out 560{lbs}/[1.23{m}*3.4{'}] and getting my result in ###{psf} as an example. I thought that the unit could be delineated by the underscore such as 34_kN but I think a start and end delineation is required for compound units like 34{kN/m^2}. There would need to be a way to force the output to a desired unit (ie. mm instead of in) like maybe setting up your desired units ahead in your sheet and then it would at least try to convert to one of those units. I think at this stage you will be charging me for the code;)
I like using Excel for my engineering calculations because I only use simpler formulas (no calculus!) and I don't want to constantly switch between Excel and Mathcad apps but use only one.
Shawn
Those are tall orders. The following sub might give you an idea for your first question:
Sub test()
Dim R As Range
Set R = Range("A1")
R.Value = "A = pr2"
R.Characters(5, 1).Font.Name = "Symbol"
R.Characters(7, 1).Font.Superscript = True
End Sub
Run it an then look at the contents of A1
As far as your second question goes - sure you can do it, but you would need to write a full-fledged expression parser. Writing one from scratch is fairly involved (at least a couple hundred lines of code) and is probably best done by using classes to create a custom tree data type then writing a recursive descent parser to parse strings into expression trees. Doable, though I have neither the time nor the inclination to do so.
I'm not quite sure what you are driving at with your last question, though my gut reaction is that it is easier than your second question since no real parsing is required and it is easy enough to create a dictionary of conversion factors.
It seems like a bit of an omission that there's no easy way to create a user-defined declarative function in Excel without defining a macro. I can't use XSLM with the uphill battle that will entail in the Enterprise, but I want to be able to define a function with intent thus.
I want to do this;
=BreakEven(C1:C20)
But I can't use a macro, although I can use a "named formula". The trouble is how to pass parameters to that? I've seen a couple of tricks (kludgy workarounds) but not for xslx.
I'd like to be able to define a Breakeven() function in another tab and reference it here passing in MORE THAN one parameter, two ranges in fact. I'm sure there's some way using string parsing but I can't see it.
I don't mind if the function doesn't look exactly like that, as long as it evaluates within the cell and I can parse it for 'intent'. For instance, this example (http://www.jkp-ads.com/articles/ExcelNames09.asp) which I was unable to get to work in xlsx uses this syntax;
=IF(ROW(D3),CellColor)
Where "cellcolor" is the name of the function and D3 is the range parameter. The other solution I'm toying with is to define a function in column format with a variable argument list (this is two rows of an excel spreadsheet);
[Value][function][parameter1][parameter2][parameter3]
24050 BreakEven C1:C20 A1:A20
It's not pretty, but the benefit of the latter is that it describes the function to an external reader. We know it's a breakeven function, whereas if we put the actual formula "OFFSET,INDIRECT,SUM()()()()etc" it would not be readable/parseable. Of course, in that case, I'd have to construct the value field by parsing the cells to the right in Excel, which would make the Value formula messy but at least it would be a self-describing row.
Can anyone suggest a better method?
Poor-man's UDF
So I think what we're going to have to do is this;
A B C D E
1 [Value][function][parameter1][parameter2][parameter3]
2 24050 BreakEven C1:C20 A1:A20
3 111 mySum 1 10 100
Where "BreakEven" is a "named function". Here's the formula for "mySum";
=sum(C1:E1)
To evaluate functions listed in B, we just put this in column A (transposing the same value for all rows in column A;
=value(B)
This works because A2 and A3 both evaluate column B as a value, which causes BreakEven and Sum to run (as poor-man's UDFs) in the context of A2 and A3. The range (C1:E1) is relative of course.
So in effect, we can write any function name in column B (as long as there's a corresponding named function defined in the workbook which can be as complex as you like). Columns C, D and E act as the parameters for the function on the same row.
I would have loved to just be able to write the following in column A instead;
=mySum(1,10,100)
But in the absence of that support, the mechanism above serves to provide a readable parameterised function that would be understandable by a user, that's also machine readable (works in CSV too) and allows us to offload our re-usable functions to a library sheet somewhere in the workbook for maintenance.
Not perfect, but an acceptable compromise, unless anyone has a clever way of doing this in a single cell?
Not really an answer, but easier to illustrate here than in a comment. Although you can't rename formulas in a simplistic way - I like your suggestion actually I've never thought about that before; but then I've never worked in a non-macro environment so this has never occurred- you can add notes into the actual formula explaining what it does. For example:
=N("This is a really complex BreakEven Formula")+SUM(3,4,5)
Is a perfectly valid formula. As I said, not really an answer, but could potentially add clarity to a complex formula
You can do this with a small trick
For example to create effectively a cuberoot UDF that emulates =cuberoot(x) then name a variable as cuberoot with a 'value' like this.
=(RC[-1])^(1/3)
Now you can either do this using a temporary switch to RC mode, or put the cursor in say cell E5 and type the name value as =(D5)^(1/3)
Now whenever you need a cuberoot you can put the argument in any cell and put =cuberoot in the cell to its right. It really works and follows true Excel rules.
I use it for multiparameter models that have the single 'argument' Time as a dependent variable. I then define the term Model as the model equation eg =a+bTime+cTime^2
where a,b,c are already named locations holding unique parameter values -
and then define Time as =RC[-1]
My sheets are filled with cells simply saying =Model and have the required time value to the left (ie their argument). It is simple to extend to multi arg functions using multiple cells. It usually fits in well with spreadsheet layouts. Change the definition of your model once in the define name box and all places change simultaneously.
I have a function called ToDMS which takes the decimal degree value in the preceding cell and converts it to a deg Min and Sec string - very tidy.
You need the degrees to be in a single cell but want it in the alt. form in another cell
elegant, simple and it works
Bob Jordan