module Main where

main :: IO()
main = putStrLn (buildWhere ["term1", "term2", "term3", "term4"])

buildWhere :: [String] -> String
buildWhere terms =
“<Where>” ++ orMany (map eqClause terms) ++ “</Where>”

type Clause = String

eqClause :: String -> Clause
eqClause term =
“<Eq>” ++
” <FieldRef Name=’MyField’ />” ++
” <Value Type=’LookupMulti’>” ++ term ++ “</Value>” ++
“</Eq>”

orClause :: Clause -> Clause -> Clause
orClause left right =
“<or>” ++ left ++ right ++ “</or>”

orMany :: [Clause] -> Clause
orMany [] = “”
orMany [x] = x
orMany (x:xs) = orClause x (orMany xs)

– More idiomatic Haskell would have replace the last two lines with:
– orMany (x:xs) = foldl orClause x xs
– but did not for clarity, as readers may be unfamiliar with Haskell

After pretty printing using another tool I get:

<Where>
<or>
<Eq> <FieldRef Name=”MyField”/> <Value Type=”LookupMulti”>term1</Value></Eq>
<or>
<Eq> <FieldRef Name=”MyField”/> <Value Type=”LookupMulti”>term2</Value></Eq>
<or>
<Eq> <FieldRef Name=”MyField”/> <Value Type=”LookupMulti”>term3</Value></Eq>
<Eq> <FieldRef Name=”MyField”/> <Value Type=”LookupMulti”>term4</Value></Eq>
</or>
</or>
</or>
</Where>

So who wins? Haskell or C#. It is properly a matter of taste and what you are used to. But to me, the Haskell solution is a lot clearer. It also seperates concerns better. The or-ing together of terms are seperated from building equal-terms. However, C# do shine when it comes to multi-line strings. It do seem strange to me that not all general purpose language has a construct similar to C# multiline stirngs.