Author | Lightnews

Mark Seemann @ploeh.dk · 11h

#repostfriday When to refactor: blog.ploeh.dk/2022/09/19/w...

When to refactor

FAQ: How do I convince my manager to let me refactor?

blog.ploeh.dk

Mark Seemann @ploeh.dk · 2d

TIL how to FOCUS the Visual Studio Code hover window.

I've long known that Ctrl+k,Ctrl+i shows hover information (e.g. type, documentation), but this hover window sometimes contains so much text that you have to scroll it. How to do that without the mouse? Press Ctrl+k,Ctrl+i again!

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Mark Seemann @ploeh.dk · 4d

New article: Empirical test-after development. blog.ploeh.dk/2025/10/27/e...

Empirical test-after development

A few techniques for situations where TDD is impractical.

blog.ploeh.dk

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Mark Seemann @ploeh.dk · 7d

Two years ago I wondered if software was getting worse. These days, however, it just seems as though updates are becoming increasingly irrelevant. I really don't care that I can add artificial bunnies to pictures 🙄 #repostfriday blog.ploeh.dk/2023/07/24/i...

Is software getting worse?

A rant, with some examples.

blog.ploeh.dk

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Mark Seemann @ploeh.dk · 9d

Indeed, conceptually there's little difference.

I may have misunderstood you, but usually when people bring up Fluent Interfaces, the main value is discovery. By entering a dot, an IDE can list possible methods you can call.

You don't get that with idiomatic F# or Haskell.

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Mark Seemann @ploeh.dk · 11d

It might have been worth mentioning too. That part is syntax-dependent, though. It works in languages that encourage 'dot-driven development', but not so much in others, like F# or Haskell.

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Mark Seemann @ploeh.dk · 11d

New article: Epistemology of software. blog.ploeh.dk/2025/10/20/e...

Epistemology of software

How do you know that your code works?

blog.ploeh.dk

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Mark Seemann @ploeh.dk · 14d

True, I forgot about that, but that should have been included as well.

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Mark Seemann @ploeh.dk · 16d

New article: Result isomorphism. blog.ploeh.dk/2025/10/15/r...

Result isomorphism

Result types are roughly equivalent to exceptions.

blog.ploeh.dk

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Mark Seemann @ploeh.dk · 21d

#repostfriday Changing your organisation. blog.ploeh.dk/2021/12/20/c...

Changing your organisation

Or: How do I convince X to adopt Y in software development?

blog.ploeh.dk

Mark Seemann @ploeh.dk · 23d

Other readers are showing their appreciation of ploeh blog by supporting it. You, too, can do that. blog.ploeh.dk/support

Support the blog

Ploeh blog is free, and always has been. Keep it free.

blog.ploeh.dk

Mark Seemann @ploeh.dk · 24d

This post, btw, rounded a corner of a sorts.

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Mark Seemann @ploeh.dk · 25d

There used to be more 'engagement' in the past. People would repost, respond, or comment on SoMe (mostly Twitter), and believe it or not, add comments to the articles themselves.

There's not much of that left now. A bit, but noticeably less than a few years ago.

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Mark Seemann @ploeh.dk · 25d

New article: Shift left on x. blog.ploeh.dk/2025/10/06/s...

Shift left on x

A difficult task may be easier if done sooner.

blog.ploeh.dk

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Mark Seemann @ploeh.dk · 28d

Thank you, that's good to hear.

To be honest, blogging increasingly feels like no-one's reading...

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Mark Seemann @ploeh.dk · 28d

#repostfriday Unit testing private helper methods. blog.ploeh.dk/2021/09/13/u...

Unit testing private helper methods

Evolving a private helper method, guided by tests.

blog.ploeh.dk

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Mark Seemann @ploeh.dk · Oct 1

Not quite, but on the other hand, I currently don't actively seek conference appearance. I'll come if invited and we can agree on terms.

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Mark Seemann @ploeh.dk · Oct 1

I've been reviewing some Python code that uses Result return types (via returns.readthedocs.io), and once more I refer to @eiriktsarpalis.bsky.social's excellent article 'You’re better off using Exceptions': eiriktsarpalis.wordpress.com/2017/02/19/y...

returns 0.26.0 documentation

returns.readthedocs.io

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Mark Seemann @ploeh.dk · Sep 30

As things currently look, IT Days in Cluj-Napoca is going to be my only public appearance in 2025. www.itdays.ro

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Mark Seemann @ploeh.dk · Sep 29

New article: Composing pure Haskell assertions. blog.ploeh.dk/2025/09/29/c...

Composing pure Haskell assertions

With HUnit and QuickCheck examples.

blog.ploeh.dk

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Mark Seemann @ploeh.dk · Sep 26

#repostfriday Property-based testing is not the same as partition testing. blog.ploeh.dk/2021/06/28/p...

Property-based testing is not the same as partition testing

Including an example of property-based testing without much partitioning.

blog.ploeh.dk

Mark Seemann @ploeh.dk · Sep 22

It's striking so quickly the industry forgets that lines of code isn't a measure of productivity. blog.ploeh.dk/2025/09/22/i...

It's striking so quickly the industry forgets that lines of code isn't a measure of productivity

Code is a liability, not an asset.

blog.ploeh.dk

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Mark Seemann @ploeh.dk · Sep 19

True. That, however, is not really my concern. Whether I have to edit 1 or 2 Repository implementations is a small problem compared to having to edit n tests. That's what I meant by O(1) edits versus O(n) edits.

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Mark Seemann @ploeh.dk · Sep 19

While you wait for your work language to get discriminated unions: Your language already has discriminated unions. #repostfriday Visitor as a sum type. blog.ploeh.dk/2018/06/25/v...

Visitor as a sum type

The Visitor design pattern is isomorphic to sum types.

blog.ploeh.dk

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Mark Seemann @ploeh.dk · Sep 17

If one were concerned about boundary cases, it might be reasonable to augment the test suite with some property-based tests, or perhaps even better, add mutation testing.