I had written this article for the “Spreadsheets” edition (#84, published September last year) of my magazine De Programmatica Ipsum, before opting to pen another (much more appropriate methinks) about Felienne Hermans; but I still like this one, so here it goes in its entirety.
In this magazine we marvel at the various strategies that society has used in the past 80 years to explain Computer Science topics to laymen. Bridging C. P. Snow’s Two Cultures, or making the impossible dialog possible, is the explicit obsession of the writer of the lines you are reading now; and this month’s Vidéothèque movies are another such attempt, and brilliant ones at that.
Leila Gharani is a very popular Iranian-Austrian-Canadian podcaster based in Amsterdam, who has become one of the focal points for Excel training and knowledge, with almost 3 million subscribers as the time of this writing. She has specialized in Microsoft Excel for the past decade, occasionally posting content about other productivity applications like PowerPoint, Teams, or even Windows. She has been covering each and every feature and function of Excel in extensive detail for the past decade, targeting business users who are interested in the latest features or in knowing how to optimize their workflows.
Behold the key phrase in the last sentence: “targeting business users”. Her audience is specifically not software engineers, programmers, or computer science majors (although she has published content targeting mechanical engineers), but rather good old users, you know, the members of that unknown species of humans that is actually trying to figure out how to make things with the software we write and publish.
Yes, the ones for whom the word “Currying” is probably something related to food.
So how do you explain lambdas to people? Have you ever tried explaining what you did for a living to your grandparents? This is not a trivial problem; some self-taught developers (like the one you are reading now) have resorted to reading various textbooks, coupled with endless programming sessions until the “coin dropped”. Others might have followed extensive training, both in university or in other contexts, and might have a stronger theoretical background.
In her videos, Ms Gharani speaks to the proverbial user, that someone who need to get stuff done, and her focus is entirely practical. She starts by showing what you can do with lambdas; in her case, cleaning up a long list of data (admittedly, a quite common task prior to being able to analyze such data), and then also in the following analysis phase, ordering items following complex rules.
It is only after showing what you can do with it, that Ms Gharani moves into the actual coding phase. In my opinion, this is an often overlooked approach in programming videos, that many a programming tutor would be wise to follow: if you are going to explain a concept, show it in action first. So that is what she does, in two steps. The first Vidéothèque video of this month features Ms Gharani introducing Excel lambdas to her audience; the second one shows her getting into the slippery topic of recursion.
So what is a lambda for Ms Gharani? She explains it in her own words at minute 04:54 of the first video:
These are just functions that you create. These functions act like machines. Once you’ve created that machine you can put through it other ingredients and reuse it as often as you want.
Simple and to the point. She goes on to show how to create lambdas, without getting into any theory or name-dropping Alonzo Church not even once. Lambdas are functions that create other functions, and yes, she literally performs some function currying in real time on screen (of course she does not say that).
Would this pass for a PhD degree in Computer Science? Are we even formally demonstrating that Excel is Turing-Complete? Of course not, and that is not the point. Her audience is not programmers; it is accountants, financial managers, assistants, associates, and whoever needs to use Excel in a daily basis to solve real-world problems.
Her second video on the subject goes even deeper, dealing with recursion. Now, I do not know about you, but when I was first exposed to recursion (around 1994 during my Turbo Pascal classes at the University of Geneva) I found the concept very, very hard to grasp at first; let alone to debug and to implement.
And I have to be honest; Ms Gharani explained recursion in this video much better than my teacher at the time. Some things are better explained by examples, at least when it comes to my brain.
Watch this month’s Vidéothèque movies, “Excel Lambda - How & when you should use it” and “Excel Recursive Lambda - Create loops with zero coding!”, and “What’s Python in Excel + Do You Really Need it?” by Leila Gharani, on her YouTube channel. Complement these videos with other gems like “Pure Functional Programming in Excel”, a conference talk by Felienne Hermans at GOTO Amsterdam 2016; Kevlin Henney ranting about Microsoft developers adding lambda calculus to Excel during the pandemic; and last but not least, a 2015 interview of Dan Bricklin and Bob Frankston by Business Insider.