4 ms·

Can someone smarter than me explain what it means to be a “purely functional” package manager? Because it’s confusing to use the term this way. In programming

Can someone smarter than me explain what it means to be a “purely functional” package manager? Because it’s confusing to use the term this way. In programming “purely functional” means no side effects; writing files to disk and mutating the state of the host system is a strong set of side effects.

esrh 4y ago
My interpretation is that the same initialization config will lead to the same setup every time, in the sense that each installation is pure in a way. Of course, while it probably just works, it's only actually pure if you pin every package to a version.
zcam 4y ago
It's a bit like nix but only for emacs. Modes are downloaded/built locally and versions pinned. From there you can put in version control your pin file and update/revert updates safely. It also guarantees you get the exact same setup across machines. Paired with use-package it makes emacs configs very compact, typically you can have a single conf file + the versions file for everything related to ones setup. That makes it very easy to transport. Even if you use nix/guix it's more convenient imho to use straight.el for emacs, as it's standalone as long as emacs is available.
hypersoar 4y ago
Think of side-effects on the system user level instead of the hardware level. A functional package manager doesn't rely on, for example, globally installed libraries. It also installs packages in such a way as to not affect the operation of your system. Nix, for example, keeps everything in a private directory. If you have packages A depending on packages X, Y, and B depending on Y, Z, then A, B, X, Y, and Z will all be placed in separate directories in /nix/store. This can all be done without touching any system or user (or emacs) profiles. Hence, "no side-effects". Of course, you probably want some side-effects, so you'll put symlinks to the stuff you want in your user profile, or into a .envrc file in the root of a project.

esrh 4y ago

My interpretation is that the same initialization config will lead to the same setup every time, in the sense that each installation is pure in a way. Of course, while it probably just works, it's only actually pure if you pin every package to a version.

zcam 4y ago

It's a bit like nix but only for emacs. Modes are downloaded/built locally and versions pinned. From there you can put in version control your pin file and update/revert updates safely. It also guarantees you get the exact same setup across machines. Paired with use-package it makes emacs configs very compact, typically you can have a single conf file + the versions file for everything related to ones setup. That makes it very easy to transport. Even if you use nix/guix it's more convenient imho to use straight.el for emacs, as it's standalone as long as emacs is available.

hypersoar 4y ago

Think of side-effects on the system user level instead of the hardware level. A functional package manager doesn't rely on, for example, globally installed libraries. It also installs packages in such a way as to not affect the operation of your system. Nix, for example, keeps everything in a private directory. If you have packages A depending on packages X, Y, and B depending on Y, Z, then A, B, X, Y, and Z will all be placed in separate directories in /nix/store. This can all be done without touching any system or user (or emacs) profiles. Hence, "no side-effects". Of course, you probably want some side-effects, so you'll put symlinks to the stuff you want in your user profile, or into a .envrc file in the root of a project.