[Haskell-cafe] Using Data.String.Conversions

Galaxy Being borgauf at gmail.com
Wed Jun 30 03:18:47 UTC 2021

Sorry, but this didn't work for me. First,

$ cabal -z install --lib string-conversions
cabal: unrecognized 'install' option `-z'

however, without -z it does run and performs an install as you indicate . .
. but then the rest doesn't work, i.e.,

$ cabal repl -z
> :set -package string-conversions
<no location info>: error:
    Could not load module ‘Data.String.Conversions’
    It is a member of the hidden package ‘string-conversions-’.
    Perhaps you need to add ‘string-conversions’ to the build-depends in
your .cabal file.

However, this did work

$ stack install string-conversions
tf8-string       > using precompiled package
string-conversions> configure
string-conversions> Configuring string-conversions-
string-conversions> build
string-conversions> Preprocessing library for string-conversions-
string-conversions> Building library for string-conversions-
string-conversions> [1 of 2] Compiling Data.String.Conversions


$ stack ghci --package string-conversions

Prelude> import Data.String.Conversions as CS

Prelude CS> :t cs
cs :: ConvertibleStrings a b => a -> b

*But*, now I am able to follow your cabal way and it does work.

So this is very confusing for a beginner. But happy ending this time. Any
lessons I can learn from this? For example, why was this so difficult?

On Tue, Jun 29, 2021 at 6:44 PM Viktor Dukhovni <ietf-dane at dukhovni.org>

> On Tue, Jun 29, 2021 at 05:39:42PM -0500, Galaxy Being wrote:
> > My problem is I can import and expose Data.Time, but
> > Data.String.Conversions will not import to my global REPL. Any tips on
> > doing this project-based would be enlightening too.
> One thing that works is:
>     $ cabal -z install --lib string-conversions
>     Resolving dependencies...
>     ...
>     In order, the following will be built (use -v for more details):
>      - utf8-string-1.0.2 (lib) (requires build)
>      - string-conversions- (lib) (requires download & build)
>     Completed    utf8-string-1.0.2 (lib)
>     ...
>     Completed    string-conversions- (lib)
>     $ cabal repl -z
>     λ> :set -package string-conversions
>     package flags have changed, resetting and loading new packages...
>     λ> import Data.String.Conversions as CS
>     λ> :t cs
>     cs :: ConvertibleStrings a b => a -> b
>     λ>
> There are surely other ways, that you might prefer, but this should get
> you started.
> --
>     Viktor.
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Lawrence Bottorff
Grand Marais, MN, USA
borgauf at gmail.com
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