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1 (* This module implements imperative processing of XML feeds.
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2 *
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3 * Module author: Adam Chlipala
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4 *)
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5
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6 con pattern :: Type -> Type -> Type
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7 (* A pattern describes a set of XML subtrees, mapping each element of the set to
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8 * a data value. A value of type [pattern internal result] uses values of type
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9 * [internal] internally, but this API exposes no details of that usage. The
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10 * type [result] gives the type used in mappings of matched subtrees. *)
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11
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12 val null : pattern unit (variant [])
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13 (* A null pattern matches nothing, returning a value of the impossible empty
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14 * type if it ever does match. *)
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15
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16 con tagInternal :: {Unit} -> Type
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17
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18 val tag : attrs ::: {Unit} -> folder attrs -> string -> $(mapU string attrs)
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19 -> pattern (tagInternal attrs) {Attrs : $(mapU string attrs), Cdata : option string}
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20 (* A basic [tag] pattern matches a single tag with a number of required
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21 * attributes. A result value gives the attribute values and an optional
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22 * CDATA value for the text content of the tag. The [string] argument is the
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23 * tag name, and the following argument gives attribute names. *)
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24
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25 val tagA : attrs ::: {Unit} -> folder attrs -> string -> $(mapU string attrs)
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26 -> pattern (tagInternal attrs) $(mapU string attrs)
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27 (* A version of [tag] that ignores CDATA *)
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28
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29 val tagAV : attrs ::: {Unit} -> folder attrs -> string -> $(mapU (string * option string) attrs)
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30 -> pattern (tagInternal attrs) $(mapU string attrs)
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31 (* Extension of tagA with optional specification of values which attributes must
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32 * bear in order to count as a match. *)
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33
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34 val tagAO : attrs ::: {Unit} -> folder attrs -> string -> $(mapU string attrs)
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35 -> pattern (tagInternal attrs) $(mapU (option string) attrs)
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36 (* A version of [tagA] that makes each attribute optional *)
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37
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38 val tagC : string -> pattern (tagInternal []) string
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39 (* A version of [tag] that only matches tags with nonempty CDATA and returns
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40 * only that text *)
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41
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42 con childrenInternal :: Type -> {Type} -> Type
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43
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44 val children : parentI ::: Type -> parent ::: Type -> children ::: {(Type * Type)}
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45 -> pattern parentI parent -> $(map (fn (i, d) => pattern i d) children) -> folder children
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46 -> pattern (childrenInternal parentI (map fst children)) (parent * $(map snd children))
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47 (* A combinator that takes in a pattern for a parent node and a set of patterns
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48 * that must be matched against children of the parent. This combinator will
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49 * find at most one match per matching parent node. *)
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50
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51 val childrenO : parentI ::: Type -> parent ::: Type -> children ::: {(Type * Type)}
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52 -> pattern parentI parent -> $(map (fn (i, d) => pattern i d) children) -> folder children
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53 -> pattern (childrenInternal parentI (map fst children)) (parent * $(map (fn (i, d) => option d) children))
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54 (* A version of [children] where each child pattern need not be matched *)
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55
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56 datatype required t = Required of t | Optional of t
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57 (* Used for marking items as required or optional. *)
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58
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59 val childrenO' : parentI ::: Type -> parent ::: Type -> children ::: {(Type * Type)}
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60 -> pattern parentI parent -> $(map (fn (i, d) => required (pattern i d)) children) -> folder children
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61 -> pattern (childrenInternal parentI (map fst children)) (parent * $(map (fn (i, d) => option d) children))
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62 (* A version of [children] where the caller marks each child pattern
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63 * as either required or optional. *)
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64
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65 con treeInternal :: Type -> Type -> Type
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66
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67 val tree : parentI ::: Type -> parent ::: Type -> childI ::: Type -> child ::: Type
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68 -> pattern parentI parent -> pattern childI child
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69 -> pattern (treeInternal parentI childI) (parent * child)
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70 (* A combinator that takes in a pattern for a parent node and another pattern to
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71 * be matched at any depth within the parent's subtree. Unlike [children],
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72 * [tree] finds as many subtree matches per parent node as possible. *)
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73
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74 con gatherInternal :: Type -> Type -> Type -> Type
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75
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76 val gather : parentI ::: Type -> parent ::: Type -> childI ::: Type -> child ::: Type
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77 -> pattern parentI parent -> pattern childI child
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78 -> pattern (gatherInternal parentI childI child) (parent * list child)
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79 (* A combinator like tree that collects matching subtree patterns into a list rather
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80 * than handling them one at a time. *)
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81
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82 type document
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83 val show_document : show document
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84 (* Type of uninterpreted XML documents *)
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85
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86 val fetch : string -> transaction document
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87 (* Retrieve a document by URL. *)
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88
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89 val app' : internal ::: Type -> data ::: Type -> acc ::: Type -> pattern internal data
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90 -> (data -> acc -> transaction acc) -> document -> acc -> transaction acc
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91 (* Find all matches of a pattern in a document, running an imperative function
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92 * on the data returned by each match while threading through some state. *)
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93
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94 val app : internal ::: Type -> data ::: Type -> pattern internal data -> (data -> transaction {}) -> document -> transaction {}
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95 (* Find all matches of a pattern in a document, running an imperative function
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96 * on the data returned by each match. *)
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