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POHow to avoid extra indentation in Template Haskell declaration quotations?
 

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  1. POHow to avoid extra indentation in Template Haskell declaration quotations?
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    <p>I have a toy program:</p> <pre><code>$ cat a.hs main = putStrLn "Toy example" $ runghc a.hs Toy example </code></pre> <p>Let's add some Template Haskell to it:</p> <pre><code>$ cat b.hs {-# LANGUAGE TemplateHaskell #-} id [d| main = putStrLn "Toy example" |] $ runghc b.hs b.hs:3:0: parse error (possibly incorrect indentation) </code></pre> <p>Right then, let's fix the indentation:</p> <pre><code>$ cat c.hs {-# LANGUAGE TemplateHaskell #-} id [d| main = putStrLn "Toy example" |] $ runghc c.hs Toy example </code></pre> <p>A single space is enough, but I do have to indent both trailing lines.</p> <p>Can I avoid having to indent most of my module? (My Real Modules have much more than a single line of code.) (And without using <code>{ ; ; }</code> notation?)</p> <p>I do want <em>all</em> of the module declarations to be captured in the quotation — in normal code I can replace <code>(...)</code> with <code>$ ...</code>, is there some equivalent of <code>[d|...|]</code> that would let me avoid the close brackets and also the indenting?</p> <p>Or is there some way module <em>A</em> can say that the top-level declarations of any module <em>B</em> that <em>A</em> is imported into are automatically processed by a function <em>A</em> exports?</p> <p>Notes:</p> <ol> <li>The Template Haskell in my Real Program is more complex than <code>id</code> — it scans the declarations for variable names that start <code>prop_</code>, and builds a test suite containing them. Is there some other pure Haskell way I could do this instead, without directly munging source files?</li> <li>I'm using GHC v6.12.1. When I use GHC v7.0.3, the error for b.hs is reported for a different location — <code>b.hs:3:1</code> — but the behaviour is otherwise identical.</li> </ol>
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    1. USdave4420
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    1. COI don't know why GHC ever insists on extra indentation, but why not sidestep a problem and use a file quoter? Perhaps write one that accepts a complete module file, with the `module ... where` header, and spits out its top-level declarations.
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    2. CO@n.m. What's a file quoter? Also, remember that you can't generate import declarations, fixity declarations and some other stuff with TH.
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      1. USJonas Duregård
    3. CO@Jonas Duregård: I'm sorry, I have just made up the term. It's something you get with a `quoteFile` and a quasi-quoter. However I was under an impression that there's a library-provided quasi-quoter that works just like `[d|...|]`, but now it looks like it's not the case.
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