haskell - 无法编译 Haskell 程序 ("Couldn' t 匹配“错误)

Question

我正在尝试实现 John MacFarlane 的 Haskell 解决方案 here ，这应该允许我将带有 MathJax( latex )输入的 HTML 文件转换为 .tex，同时保留数学。脚本是:

import Text.Pandoc

main = toJsonFilter fixmath

fixmath :: Block -> Block
fixmath = bottomUp fixmathBlock . bottomUp fixmathInline

fixmathInline :: Inline -> Inline
fixmathInline (RawInline "html" ('<':'!':'-':'-':'M':'A':'T':'H':xs)) =
  RawInline "tex" $ take (length xs - 3) xs
fixmathInline x = x

fixmathBlock :: Block -> Block
fixmathBlock (RawBlock "html" ('<':'!':'-':'-':'M':'A':'T':'H':xs)) =
  RawBlock "tex" $ take (length xs - 3) xs
fixmathBlock x = x

我安装了 64 位 OSX 版本的 Haskell，还给出了命令 cabal install pandoc 来获取 pandoc 函数。但是，在执行

ghc --make fixmath.hs

我收到以下错误:

[1 of 1] Compiling Main             ( fixmath.hs, fixmath.o )

fixmath.hs:9:26:
    Couldn't match expected type `Format' with actual type `[Char]'
    In the pattern: "html"
    In the pattern:
      RawInline "html"
                ('<' : '!' : '-' : '-' : 'M' : 'A' : 'T' : 'H' : xs)
    In an equation for `fixmathInline':
        fixmathInline
          (RawInline "html"
                     ('<' : '!' : '-' : '-' : 'M' : 'A' : 'T' : 'H' : xs))
          = RawInline "tex" $ take (length xs - 3) xs

fixmath.hs:10:13:
    Couldn't match expected type `Format' with actual type `[Char]'
    In the first argument of `RawInline', namely `"tex"'
    In the expression: RawInline "tex"
    In the expression: RawInline "tex" $ take (length xs - 3) xs

fixmath.hs:14:24:
    Couldn't match expected type `Format' with actual type `[Char]'
    In the pattern: "html"
    In the pattern:
      RawBlock "html"
               ('<' : '!' : '-' : '-' : 'M' : 'A' : 'T' : 'H' : xs)
    In an equation for `fixmathBlock':
        fixmathBlock
          (RawBlock "html"
                    ('<' : '!' : '-' : '-' : 'M' : 'A' : 'T' : 'H' : xs))
          = RawBlock "tex" $ take (length xs - 3) xs

fixmath.hs:15:12:
    Couldn't match expected type `Format' with actual type `[Char]'
    In the first argument of `RawBlock', namely `"tex"'
    In the expression: RawBlock "tex"
    In the expression: RawBlock "tex" $ take (length xs - 3) xs

出了什么问题，我该怎么办？

Answer 1

最新版本的 pandoc 更改了 RawBlock 和 RawInline 的“格式”类型。如果将 "html" 和 "tex" 替换为 (Format "html") 和 (Format "tex")，你应该没问题。 (假设除了编译器标记的问题之外没有其他问题。)