Comment by ravi-delia | Hacker News Reader

Comment by ravi-delia | Hacker News Reader

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There's a place for both even with a REPL I think. Sometimes when I'm tracking a bug down or writing a new function against an old one, I find that I'm writing little one-off functions or worse, replicating a function body line by line in a let block to simulate arguments. Once I opened up a project and realized I wanted one of them, but it was lost when the REPL closed. I literally got as far as opening another file to stow these little utilities before I realized I had reinvented bargain-bin testing.

My dream is still to come up with some ergonomic way of blending the two. I want to have tests written, but swap out the thing they test live in the REPL. Or register new one-off tests from the REPL for things I don't think will be useful once things are set in stone. I've heard one of the several billion testing frameworks for common lisp does something like this, but I haven't checked it out yet.

> Once I opened up a project and realized I wanted one of them, but it was lost when the REPL closed.

You don't type directly in the REPL most of the time. Send lines and functions to it instead.

Ohhh, I wondered why people were so hyped about that! In my head I rounded it off to not wanting to recompile the whole file- I should have realized how dumb that was. This actually makes a lot of sense. When I helped a friend set up Calva, a part of me was really just assuming it was misconfigured- but no, it's designed to facilitate this kind of editing.

Though, I must ask, is it really that much better? I do keep functions around if I think I'll have a use for them again- the vast vast majority really are one-offs. Plus, most of my REPL usage is iterating on an expression. Obviously it's handy to edit it in place, but it's nice having multiple versions, even multiple trees, without having to relocate a cursor or undo unrelated changes.

> Though, I must ask, is it really that much better?

Yes, it is.

> Obviously it's handy to edit it in place, but it's nice having multiple versions, even multiple trees, without having to relocate a cursor or undo unrelated changes.

You can do both.

I almost always do my repl work in a source code file. That way I never lose it when the repl closes and I can copy it into a test when I know what’s going on.

[see cousin comment for my admission of stupidity]

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