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Fix example code in the tutorial #2100

Merged
merged 3 commits into from
Dec 4, 2020
Merged

Fix example code in the tutorial #2100

merged 3 commits into from
Dec 4, 2020

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jeremyschlatter
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@jeremyschlatter
Fix example code in the tutorial
b3a55dd
@jeremyschlatter
Fix more example code in tutorial
584b97c 
- `Dhall.expected resultDecoder` is a `Validation Expected TypeErrors (Expr Src Void)`,
  not a `Expr Src Void`. `maximum` is a terse way of extracting the
  `Expr Src Void` or crashing in the error case. (And in this example,
  it is never the error case.)

- ++ works for String, but not Data.Text. Use the Semigroup instance
  instead.
@jeremyschlatter
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The changes here allowed me to compile and run the example Haskell code. The code does not seem to work as described, though. In particular this claim

Now we can omit the definition of Result in our example.dhall file. While this will work perfectly...

seems to be false. When I change example.dhall to be

-- example.dhall

Result.Failure +1

and then parse it with

Dhall.input (Dhall.auto :: Dhall.Decoder Result) ("let Result = " <> Data.Text.pack resultTypeString <> " in ./example.dhall")

I get this failure:

main: 
↳ ./example.dhall

Error: Unbound variable: Result

Gabriella439
Gabriella439 approved these changes Nov 21, 2020
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@jeremyschlatter: Yeah, that part of the documentation is incorrect. Bound variables are not forwarded to transitive imports. Would you like to also delete that part as part of this pull request?

@Gabriella439 Gabriella439 merged commit 95ba4e8 into dhall-lang:master Dec 4, 2020
@jeremyschlatter jeremyschlatter deleted the tutorial-fix branch March 23, 2022 20:37
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@Gabriella439 Gabriella439 Gabriella439 approved these changes

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@jeremyschlatter @Gabriella439