LET is not ‘new’

Was the ‘New World’ of 1492 actually new?

Since its announcement, I have now seen more than 10 videos and articles that demonstrate the new LET function in Excel.

It’s just a suggestion, why not explain why the new feature is better than what we already have? Argue the case for using the new feature instead of what we already have? In what circumstances is the new feature usable? Perhaps even venture into why Microsoft decide to bring out an alternative, for those interested in the philosophical aspects of the new possibilities?

By not mentioning it, the audience is left thinking that LET never existed before.

Custom Formulas

Excel 5 introduced Custom Formulas to the spreadsheet world in 1994. This meant that, spreadsheet users can now create their own formulas. This had many advantages, such as reducing a long complex one to a simple one that can be replicated and reused, thus reducing risk. Such as laying out the logic of the formula clearly, and well commented.

So, what is the new LET?

The new LET formula enables us to include a variable within a formula. However, variables are normal in a Custom Formula. So, LET in formulas was with us since 1994.

LET a = b + c

However, as we know, the keyword LET is optional; it is assumed when we say.

a = b + c

This could be a reason why the occurrence of LET (a simple assignment) as a keyword is not something we see anymore. Perhaps that could be the reason why the very existence of LET is not fully appreciated.

Anyone who cut his/her teeth on a Sinclair or BBC home computer back in the day will have LET deeply embedded in their minds. LET was (just about!) the very first keyword we saw. A simple assignment was the very first concept we learned.

(Do I remember this correctly? Did the Sinclair Spectrum ad have the LET keyword rubber-button prominently placed front and centre in the magazine ad?)

Current Education

Not only is the presenter not referring to the essential points I started with, no one is even asking how the new LET (in formulas) is better than LET in a Custom Formula. It’s not an easy question to ask, when the headline hails the feature as a ‘new’ feature. To do so is to challenge the very premise of the presentation, I feel.

I would suggest, and you may have a better way putting this, ‘the new LET allows us to include an intermediate value to be included withing a formula in a variable. This is practical in simple scenarios. LET in Custom Formulas still exist, and can continue to be used in cases where many intermediate calculations are needed, and the logic needs to be explained transparently. The new feature of LET used in any scenario that’s not ‘simple’ is impractical’.

But, of course, this is a long way from acknowledging that LET has always existed as a fundamental necessity of calculation logic.

New World

The ‘New World’ discovered in 1492 was ‘new’ to those that discovered it, only because they didn’t know that it always existed.

Native Americans never called The Americas the New World. But (understandably) the Europeans who discovered it referred to it as ‘new’ in order to communicate to other Europeans who didn’t know.

One thing we all can agree on is, The Americas didn’t suddenly rise out of the ocean in 1492 😉

An Example of LET

[TBA] Example from a ‘Financial Modelling’ book I’m technical editing at the moment. There’s a nested IF formula that’s hard to figure out just by looking at it. Whereas, a Custom Formula sets it out clearly. In this example, there’s a grid of data that is assigned to an array (a LET), and three other single value variables that point to specific cells (with LET). But, of course, you don’t see ‘LET’ in the code because LET is assumed in VBA.

The Custom Formula is far easier to use and understand than the messy formula with nested IFs.