Xml in Standard ML

Here’s the translation of the XML handling example from Go to Standard ML:

(* Standard ML offers XML handling through libraries like SML/NJ's XML library *)

structure XML = XML

(* Define a datatype to represent a plant *)
datatype plant = Plant of {id: int, name: string, origin: string list}

(* Function to convert a plant to a string representation *)
fun plantToString (Plant {id, name, origin}) =
    "Plant id=" ^ Int.toString id ^ ", name=" ^ name ^ ", origin=" ^ 
    String.concatWith "," origin

(* Function to create an XML element *)
fun createXMLElement name attrs content =
    XML.Element (name, attrs, content)

(* Function to create an XML attribute *)
fun createXMLAttr name value =
    XML.Attr (name, value)

(* Function to convert a plant to XML *)
fun plantToXML (Plant {id, name, origin}) =
    createXMLElement "plant" 
        [createXMLAttr "id" (Int.toString id)]
        [createXMLElement "name" [] [XML.Text name],
         createXMLElement "origin" [] (map (fn o => XML.Text o) origin)]

(* Function to parse XML into a plant *)
fun xmlToPlant xmlElem =
    case xmlElem of
        XML.Element ("plant", attrs, children) =>
            let
                val id = valOf (Int.fromString (XML.getAttrValue "id" attrs))
                val name = XML.getChildText "name" children
                val origin = map XML.getText (XML.getChildrenByTagName "origin" children)
            in
                Plant {id = id, name = name, origin = origin}
            end
      | _ => raise Fail "Invalid XML structure for Plant"

(* Main function *)
fun main () =
    let
        val coffee = Plant {id = 27, name = "Coffee", origin = ["Ethiopia", "Brazil"]}
        
        (* Convert plant to XML *)
        val coffeeXML = plantToXML coffee
        val _ = print (XML.toString coffeeXML ^ "\n")
        
        (* Add XML header *)
        val _ = print ("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" ^ 
                       XML.toString coffeeXML ^ "\n")
        
        (* Parse XML back to plant *)
        val parsedPlant = xmlToPlant coffeeXML
        val _ = print (plantToString parsedPlant ^ "\n")
        
        (* Create nested XML structure *)
        val tomato = Plant {id = 81, name = "Tomato", origin = ["Mexico", "California"]}
        val nested = createXMLElement "nesting" []
            [createXMLElement "parent" []
                [createXMLElement "child" []
                    [plantToXML coffee, plantToXML tomato]]]
        val _ = print (XML.toString nested ^ "\n")
    in
        ()
    end

(* Run the main function *)
val _ = main()

This Standard ML code demonstrates XML handling, which is conceptually similar to the original Go example. Here’s a breakdown of the key points:

We define a plant datatype to represent the plant structure.
Functions like plantToString, createXMLElement, and createXMLAttr are implemented to handle XML creation and conversion.
plantToXML converts a plant to an XML structure, while xmlToPlant parses XML back into a plant.
The main function demonstrates creating plants, converting them to XML, parsing XML, and creating nested XML structures.
Standard ML doesn’t have built-in XML support like Go, so we’re using a hypothetical XML structure that would be provided by an XML library.
Error handling is simplified in this example. In a real-world application, you’d want to add more robust error checking and handling.
The nested XML structure is created using the createXMLElement function, mirroring the nested structure in the original Go example.

To run this program, you would need to have an SML compiler and an XML library installed. The output would be similar to the Go example, showing the XML representations of the plants and the nested structure.

Note that Standard ML’s ecosystem doesn’t have as comprehensive built-in XML support as Go, so in practice, you might need to use additional libraries or implement more XML handling functions yourself.

Json in Standard ML

Time in Standard ML

Learn X By Example

Title here

Xml in Standard ML