PureScript noob question, plus not defined in repl

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#1

I am completely new to PureScript and am doing chapter 3 of the Freeman book.

When I run spago repl
and type

> 1 + 3
Error found:
in module $PSCI
at :1:3 - 1:4 (line 1, column 3 - line 1, column 4)

  Unknown operator (+)


See https://github.com/purescript/documentation/blob/master/errors/UnknownName.md for more information,
or to contribute content related to this error.

Seriously? If I run the repl in another directory, it works as expected.

What is going on?

1 Like
#2

Hello and welcome to PureScript.

It’s a bit strange I guess but you have to import the prelude:

import Prelude

PureScript itself is a rather slim language and most things come with packages - and it happens that + is only defined in one as well.
Luckily most of this basic stuff is packaged together in Prelude but you have to import it as there is no auto-import of this.

EDIT: well I guess there is some auto-import now (just noticed it :smile: ) - if you see the import Prelude after starting you are good to go.
I’m sure someone here knows exactly when this is used … cannot find it right now but I’ll keep looking :wink:

#3

Ok I think when you do spago init it should generate a .purs-repl file that get’s loaded and this should include the import Prelude part.
If you have no such file a default is used include the import.

So in the directory where it is not working for you is there such a file and what is it’s content?

#4

There is no such file. And you’re right, the import Prelude did it.

I just cloned the book repo.

Funny thing it works in other directories with no such file…

#5

if you want you can add it (just add a single line import Prelude) so that you don’t have to retype it.

I guess spago will assume some default outside a project directory (spago.dhall etc. present).

#6

That might be the case.

Thanks for the help, appreciate the swift response.

#7

It might be nice to add a .purs-repl file with the same content inside the book repo, as (+) probably would have just worked without needing to be imported in that case.

2 Likes
#8

So if that file is in the root of the repo, it will be found no matter were I start spago repl ?

1 Like
#9

I think it needs to be in the same directory, so perhaps we could add one to each directory that you’re likely to be running the repl from?