Unknown value abs

cgodgers · December 25, 2020, 7:50pm

Hello dear community!

A really newbie question, but I can’t figure out why does this happen.

Reading the prelude docs, I’d expect that the abs function would be imported in the REPL whenever I import Prelude into it.

However, that’s not the case. Even more, greaterThan isn’t aswell imported, but min is (refering to Prelude’s Data.Ord). Whenever I try to use abs I get an Unknown value error. Ofc I can solve that by

Am I getting something wrong?

cgodgers · December 25, 2020, 7:53pm

Oh, nevermind, solved it.

Is just that I didn’t know how to read Pursuit docs

Should’ve seen this page to see what is actually imported from Prelude.

milesfrain · December 26, 2020, 8:58pm

I got tripped-up by this as well https://github.com/purescript/purescript-prelude/issues/222

cgodgers · December 27, 2020, 11:43am

Yeah it’s quite strange, but there’s its own reasoning.

For no more surprises I may try this cute little pattern:

github.com

JordanMartinez/purescript-jordans-reference/blob/latestRelease/31-Design-Patterns/20-Project-Prelude.md

# Project Prelude

If you ever find yourself thinking, "I wish `<ModuleName>` was in `Prelude`," or "I wish I didn't have to import `<ModuleName>` in each PureScript file," this design pattern is for you.

PureScript files can often have a lot of lines for just the import statements. While it makes it easier to see which function is being used in a given file, it can be tedious to import everything, even with tooling that enables auto-importing.

However, most projects and applications will define a project-specific Prelude to be used just in that project. Rather than typing something like this in each of your files:
```purescript
import Prelude

import Effect (Effect)
import Effect.Class (class MonadEffect, liftEffect)
import Effect.Aff (Aff, launchAff_)
import Effect.Aff.Class (class MonadAff, liftAff)
import Control.Monad.Reader.Class (class MonadReader, ask, local)
import Control.Monad.State.Class (class MonadState, get, put, modify_)
import Data.Array ((:), (!!))
import Data.Bifunctor (class Bifunctor, bimap, lmap, rmap)
import Data.Maybe (Maybe(..), maybe, fromJust)
import Data.Newtype (class Newtype, un)

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Hope that this helps some people

ajnsit · December 27, 2020, 1:20pm

Since spacemacs’ Purescript support is so good, I tend to import everything explicitly. It also helps me remember the location of everything better.

In Spacemacs SPC-m-m-i-a will import the symbol currently under the cursor for you.

milesfrain · December 27, 2020, 8:34pm

Yes. This is only an issue outside of IDEs (e.g. REPL and Try PureScript).