Executable within a library and while using the same library in cabal - haskell

Question

This is my first try at an open source project, but I still can't get the right way to set up my .cabal file.
I have have library, an executable and a (soon to come) test config.
I want to use the library and within the executable, so the both of them can be used when it gets downloaded.
I followed this guide, but I'm still struggling with the cabal-config as I only get it to work while importing everything again.
My current directory
- src/
- Main.hs
- Format/
- C.hs
- Converter.hs
- Raw.hs
- RGB565.hs
- tests/...
- dist/...
- UTFTConverter.cabal
The executable Main.hs header looks like this.
module Main where
import Format.C
import Format.Converter
The library files in Format/ look like this.
module Format.{filename} where
...
This is what the cabal file looks like.
name: UTFTConverter
...
cabal-version: >=1.10
library
exposed-modules: Format.C
, Format.Converter
, Format.Raw
, Format.RGB565
build-depends: base >=4.7 && <4.8
, filepath >=1.3 && <1.4
, directory >=1.2 && <1.3
, time >=1.4 && <1.5
, bytestring >=0.10 && <0.11
, JuicyPixels >=3.2 && <3.3
hs-source-dirs: src
...
executable UTFTConverter
main-is: Main.hs
build-depends: base >=4.7 && <4.8
, filepath >=1.3 && <1.4
, directory >=1.2 && <1.3
, time >=1.4 && <1.5
, bytestring >=0.10 && <0.11
, JuicyPixels >=3.2 && <3.3
--, UTFTConverter ==0.1 <-- this does not work
hs-source-dirs: src
...
test-suite tests:
...
Without the comment this error comes up when I cabal build.
...
cabal: At least the following dependencies are missing:
UTFTConverter ==0.1
...
It works right now, but in the tutorial the executable was using the library in the same cabal file.
executable bassbull
main-is: Main.hs
ghc-options: -rtsopts -O2
build-depends: base,
bassbull, -- <-- this is the name of the library
bytestring,
cassava
hs-source-dirs: src
default-language: Haskell2010
I know this is currently working, but I would rather use it the right way from the start. Is this the "right" way?

Answer 1

That's due to your library version being 0.1.0.0, not 0.1. They don't match up exactly, thus cabal doesn't recognize your library as a candidate. Instead, use 0.1.* or 0.1.0.0 depending on your version policy:
executable UTFTConverter
main-is: Main.hs
build-depends: base >=4.7 && <4.8
, filepath >=1.3 && <1.4
, directory >=1.2 && <1.3
, time >=1.4 && <1.5
, bytestring >=0.10 && <0.11
, JuicyPixels >=3.2 && <3.3
, UTFTConverter ==0.1.0.0
hs-source-dirs: src
References
Cabal User Guide, section "Build Information".