Conditional for pattern, a guessing game tutorial, and the reaction phase
We learn yet another Haskell idiom: the conditional for. We move on to implementing a guessing game in Haskell to understand what is meant by "most code is impure anyway". Finally, we get some wisdom from Ward about the lead time of product development.
Hello! I hope your week is going well.
New articles
Non-Obvious Haskell Idiom: Conditional For
This next non-obvious idiom is the for-loop-over-a-single-element that lets us write something like
for_ corsOrigin $ addHeader "Access-Control-Allow-Origin"
and have the header be added if the corsOrigin variable has a value, leaving the request untouched if it did not. This works because we can think of a Maybe Text as a collection of either zero or one elements, and the for_ loop iterates any collection.
Full article (2–4 minute read): Non-Obvious Haskell Idiom: Conditional For
Guessing Game: Haskell Style
The guessing game tutorial for Ada has proved popular, so here's one in Haskell. The driving force behind this is to show what I mean when I say that "most Haskell code is impure anyway". Don't let Haskell's purity be a problem – normal applications are full of side effects and Haskell works great even for side effectful code. We'll see some useful Haskell patterns along the way.
Full article (8–18 minute read): Guessing Game: Haskell Style
Flashcard of the week
I'm a fan of Ward, so here goes another question from Lean Product and Process Development.
What is the reaction phase of lead time?
Ward splits the lead time of product development up into four phases:
- Reaction
- Exploration
- Lock-in
- Fixup
Exploration should make up most of the development cycle: this is where the organisation explores various ways of solving a problem to find one approach that (a) adequately solves the problem and (b) can be built with high certainty over a constrained timeframe. Lock-in should be as short as possible, and is when the organisation has picked an approach they are confident in, and implement it fully. The fixup phase is the thing that happens after release when all kinds of problems are discovered and fixed. Hopefully this is also short.
What the reaction phase is about isn't complicated, but Ward phrased it nicely:
It is the time that passes between when an opportunity first presents itself, and when investment into that opportunity is made.
Here's a bonus question from a related flashcard:
When can the reaction time be negative?
In highly cyclical industries an organisation can start to explore the problems involved in solving the next generation of problems even before there is actual demand/opportunity to sell it.
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