Why can't I use Text.Regex in my Stack project? - haskell

Question

All I want is to parse a simple string using regex.
First question: Should I be using Text.Regex or something else? Stackage lists at least 11 regex packages. I don't care if it's PCRE or Posix. At this point I'll accept anything.
Second Question: How do I include Text.Regex in my project? This is my experience so far:
package.yaml has
dependencies:
- base >= 4.7 && < 5
- regex
stacky.yaml attempt 1
extra-deps:
- regex-1.0.1.3
Response to stack build
Error: While constructing the build plan, the following exceptions were encountered:
In the dependencies for regex-1.0.1.3:
base-compat-0.10.5 from stack configuration does not match >=0.6 && <0.10 (latest matching version is 0.9.3)
template-haskell-2.13.0.0 from stack configuration does not match >=2.7 && <2.12 (latest matching version is 2.11.1.0)
needed due to CCompiler-0.1.0.0 -> regex-1.0.1.3
Some different approaches to resolving this:
* Set 'allow-newer: true' to ignore all version constraints and build anyway.
* Consider trying 'stack solver', which uses the cabal-install solver to attempt to find some working build configuration. This can be convenient when dealing with many complicated constraint
errors, but results may be unpredictable.
* Recommended action: try adding the following to your extra-deps in /Users/adamfrank/Dev/Haskell/CCompiler/stack.yaml:
- base-compat-0.9.3
- template-haskell-2.11.1.0
Plan construction failed.
stack.yaml attempt 2
extra-deps:
- regex-1.0.1.3
- base-compat-0.9.3
- template-haskell-2.11.1.0
Response to stack build:
Error: While constructing the build plan, the following exceptions were encountered:
In the dependencies for regex-1.0.1.3:
template-haskell-2.13.0.0 from stack configuration does not match >=2.7 && <2.12 (latest matching version is 2.11.1.0)
needed due to CCompiler-0.1.0.0 -> regex-1.0.1.3
Some different approaches to resolving this:
* Set 'allow-newer: true' to ignore all version constraints and build anyway.
* Consider trying 'stack solver', which uses the cabal-install solver to attempt to find some working build configuration. This can be convenient when dealing with many complicated constraint
errors, but results may be unpredictable.
* Recommended action: try adding the following to your extra-deps in /Users/adamfrank/Dev/Haskell/CCompiler/stack.yaml:
- template-haskell-2.11.1.0
Plan construction failed.
???
It says I need to add a line I already added.
Do I need a different version of regex? If so, which one, and how do I figure that out?

Answer 1

There are a few recommendations in the comments as to what to use: regex-base, but it is also good to understand why it is not compiling.
Stackage provides a list of compatible packages in each LTS. You can alter some of the version numbers as long as they respect the version constraints of other dependencies. Not all of these dependency restrictions are well defined in the packages coming from Hackage, which is one of the reasons for using Stackage.
Generally each stackage major LTS release is associated with a particular version of GHC which also has a particular version of base. When you pick a major version of LTS, you are also picking a version of GHC and base. If you want to change GHC and/or base versions, it is easier to change the LTS version. The first thing after the LTS version on the Stackage LTS page is the GHC version number.
In your case regex requires a version of template-haskell and base-compat that violate the constraints of other dependencies.