Interpolation-0.2.4: Multiline strings, interpolation and templating.




str :: QuasiQuoterSource

Quasiquote str implements multiline strings with interpolation. Interpolating a value into the string is done by $<String expression>$ and interpolating anything with instance Show is $:<Show expression>$. Due to pretty deep limitations, the parser is not able to properly deduce associtivity of infix operators, so use lots and lots of parenthesis.

Repetitive patterns can be made with # symbol:

  #<var> in <list>: <interpolated string> (|<interpolated string>)#

Where (|<interpolated string>) denotes optional separator for the elements.

Multiline indentation is handled by aligning on smallest un-empty line after the first. Neither pattern matching nor nested #-patterns are supported, however, see example below.

Normal '\\n' style escaping of special characters is intentionally not supported. Please use $endline$ or $n$ style instead.

As an example, let's plot set of vectors with gnuplot:

   plotVecs :: [(String,[Double])] -> String
   plotVecs vs =  
       [$str| ## Plot multiple vectors
              plot #(n,_) in vs:- with lines lw 5 title $:n$ |, #
              #d in map snd vs:$singleVec d$$endline$e$endline$# |]
    singleVec n = [$str|#(e,i) in zip n [1..]: $:i$ $:e$|$endline$#|]
  *Gnuplotter> plotVecs [("A",[1..5]),("B",[2..6])]
  # Plot multiple vectors
   plot - with lines lw 5 title "A" , - with lines lw 5 title "B" 
    1 1.0
    2 2.0
    3 3.0
    4 4.0
    5 5.0

    1 2.0
    2 3.0
    3 4.0
    4 5.0
    5 6.0


endline :: StringSource

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