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XML

Parsing

Process an XML document

Given the XML Document:

<shopping>
<item name="bread" quantity="3" price="2.50"/>
<item name="milk" quantity="2" price="3.50"/>
</shopping>

Print out the total cost of the items, e.g. $14.50

python

from xml.dom.minidom import parseString
document = parseString(
"""<shopping>
<item name="bread" quantity="3" price="2.50"/>
<item name="milk" quantity="2" price="3.50"/>
</shopping>""").documentElement
total = sum([float(item.getAttribute('price')) *
int(item.getAttribute('quantity'))
for item in document.getElementsByTagName('item')])
print '$%.2f' % total

clojure

(println (format "Total cost of items are $%#.2f"
(->> (xml-seq (parse *xml-input-stream*))
(filter #(= :item (:tag %))) ; Remove all but the item tags
(map :attrs) ; Keep the attributes
(map (fn [e] (str "(* " (:quantity e) " " (:price e) ")"))) ; Get the total price as a sexp
(map read-string) ; "(* quantity price)" -> (* quantity price)
(map eval) ; (* quantity price) -> quantity*price
(apply +)))) ; Sum all elements

fsharp F# 2.0 Interactive build 4.0.30319.1

#r @"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\v3.5\System.Xml.Linq.dll"

open System
open System.Xml.Linq
//XElement Helper
let xname sname = XName.Get sname

let xmlsnippet =
let snippet = new XElement(xname "shopping")
//create bread
let bread = new XElement(xname "item")
bread.SetAttributeValue(xname "name","bread")
bread.SetAttributeValue(xname "quantity",3)
bread.SetAttributeValue(xname "price",2.50)
//add bread to snippet
snippet.Add(bread)
//create milk
let milk = new XElement(xname "item")
milk.SetAttributeValue(xname "name","milk")
milk.SetAttributeValue(xname "quantity",2)
milk.SetAttributeValue(xname "price",3.50)
//add milk to snippet
snippet.Add(milk)
snippet

let totalprice (xe: XElement) =
xe.Descendants(xname "item")
|> Seq.map(fun i -> Double.Parse(i.Attribute(xname "price").Value))
|> Seq.fold(fun acc x -> acc + x) 0.0

fsharp

let xname sname = XName.Get sname
let xattr (elem: XElement) sname = elem.Attribute(xname sname).Value
let xml = XDocument.Load("xml.txt")

let shoppingCost =
xml.Descendants(xname "item")
|> Seq.map (fun i -> Double.Parse(xattr i "quantity"), Double.Parse(xattr i "price"))
|> Seq.sumBy (fun (quantity, price) -> quantity * price)

fsharp

// Alternative solution that uses XML Navigation, and XPath expressions to ensure that
// the items have the required attributes
let xname sname = XName.Get sname
let xattr (elem: XElement) sname = elem.Attribute(xname sname).Value

let navigator = XPathDocument("xml.txt").CreateNavigator()
let path = XPathExpression.Compile("/shopping/item[@price][@quantity]")
let names = XmlNamespaceManager(navigator.NameTable)
path.SetContext(names)
let shoppingCost =
match path.ReturnType with
| XPathResultType.NodeSet ->
navigator.Select(path)
|> Seq.cast
|> Seq.map (fun (i: XPathNavigator) ->
if i.IsNode then
let elem = XElement.Parse(i.OuterXml)
Double.Parse(xattr elem "quantity"), Double.Parse(xattr elem "price")
else
failwith "Error in expression, expecting to see a node"
)
|> Seq.sumBy (fun (quantity, price) -> quantity * price)
| _ -> failwith "Error in expression, expecting to see a node set"

cpp rapidxml

char input[] =
"<shopping>"
" <item name=\"bread\" quantity=\"3\" price=\"2.50\"/>"
" <item name=\"milk\" quantity=\"2\" price=\"3.50\"/>"
"</shopping>";

xml_document<> doc;
doc.parse<0>(input);
xml_node<> *shopping = doc.first_node();

float total_price = 0;
for (xml_node<> *item = shopping->first_node(); item != NULL; item = item->next_sibling())
{
float item_sum = 0;
float val;

if (string(item->name()) != "item")
continue;

for (xml_attribute<> *attr = item->first_attribute(); attr != NULL; attr = attr->next_attribute())
{
string name(attr->name());
if (name == "quantity" || name == "price")
{
stringstream v(attr->value());
v >> val;
if (item_sum)
item_sum *= val;
else
item_sum = val;
}
}
total_price += item_sum;
}

cout.setf(ios::fixed, ios::floatfield);
cout << "Total price is $" << setprecision(2) << total_price << endl;

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