如何在函数内的Haskell中将某些内容转换为字符串

我真的是哈斯凯尔的一个笨蛋，我已经被困在一个愚蠢的函数里好几天了。 所以我有一个家庭作业，老师希望我们只修改graphviz模块实例的函数。我试图实现第一个函数，但无法将id转换为字符串（您可以通过查看graphviz模块了解原因）

这是graphviz模块（graphviz.hs）

再一次，为所有这些代码感到抱歉，我认为理解我不理解的东西是必要的

我的问题很简单：既然id不是字符串，如何实现GraphVizNodeList？？？如何将其转换为适合graphviz函数的值

---

非常感谢和抱歉

graphvizNodesList（图形弧标签样式）=[（id，label，style）| id
graphvizNodesList（图形弧标签样式）=[（id，label，style）| idI尝试过了，我在
[（show id，label，style）|中做了，或者这里show idkey是数据的函数。Map key:：Map k a->[k]，O（n）。按升序返回映射的所有键。请参阅我的新注释。我认为存在比仅将
id
转换为
String
键是数据的函数更大的错误。map
然后
id
graphvizNodesList (Graph arcs labels styles) = [(id,label,style) | id<-keys, label<-(elems labels), style<-(elems styles)]

import Data.Map (Map,empty,member,insert,keys,findWithDefault,assocs ,fromList,(!),union,mapWithKey,toList,elems)
import Graphviz 

-- | A directed graph
data Graph v = Graph
    { arcsMap :: Map v [v]     -- A map associating a vertex with its successors
    , labelMap :: Map v String -- The Graphviz label of each node
    , styleMap :: Map v String -- The Graphviz style of each node
    }
...
Some functions implemented here not important
...

...
blabla
...
-- | A triple @(id,label,style)@ where
--
-- * @id@ is the key identifying the node (must be unique)
-- * @label@ is any string compatible with Graphviz
-- * @style@ is any string describing the Graphviz style of the node
type GraphvizNode = (String, String, String)

-- | A triple @(id1,id2,label)@ where
--
-- * @id1@ is the key of the source vertex
-- * @id2@ is the key of the target vertex
-- * @label@ is the label of the arc
type GraphvizArc = (String, String, String)

-- | Class of types that can be converted to Graphviz strings
class Graphviz g where

    -- | The list of Graphviz nodes
    --
    -- It returns a list of all nodes of the graph, indicating the label and
    -- the style of each node.
    graphvizNodesList :: g -> [GraphvizNode]

    -- | The list of Graphviz arcs
    --
    -- It returns a list of all arcs of the graph, indicating the label of the
    -- arc.
    graphvizArcsList :: g -> [GraphvizArc]

    -- | The header of the Graphviz string
    --
    -- This is the string printed before writing the nodes and the arcs.
    graphvizHeader :: g -> String
    graphvizHeader _ = "digraph {\n"

blablablabla...

graphvizNodesList (Graph arcs labels styles) = [(id,label,style) | id<-keys, label<-(elems labels), style<-(elems styles)]