The MatchTree structure

The MatchTree structure provides a tree-structured representation of the result of a successful regular expression match. The tree structure corresponds to the nesting of groups in the regular expression.

Synopsis

signature MATCH_TREE
structure MatchTree : MATCH_TREE

Interface

datatype 'a match_tree = Match of 'a * 'a match_tree list

val root : 'a match_tree -> 'a
val nth : ('a match_tree * int) -> 'a (* raises Subscript *)
val map : ('a -> 'b) -> 'a match_tree -> 'b match_tree
val app : ('a -> unit) -> 'a match_tree -> unit
val foldl : ('a * 'b -> 'b) -> 'b -> 'a match_tree -> 'b
val foldr : ('a * 'b -> 'b) -> 'b -> 'a match_tree -> 'b
val find : ('a -> bool) -> 'a match_tree -> 'a option
val num : 'a match_tree -> int

Description

datatype 'a match_tree = Match of 'a * 'a match_tree list: The representation of the results of a nested grouping of regular expressions. The type variable 'a is typically instantiated to information about the particular range of the source that the node covers. For example, it might be the pair of the start position and length of the match.
val root : 'a match_tree -> 'a: root mt returns the information about the root (outermost) match in the tree.
val nth : ('a match_tree * int) -> 'a (* raises Subscript *): nth (mt, i) returns the information about the i'th match in the tree, where matches are labeled in pre-order starting with 0 for the root. This function raises the Subscript exception if i < 0 or there are fewer than i-1 nodes in the tree.
val map : ('a -> 'b) -> 'a match_tree -> 'b match_tree: map f mt returns the result of mapping the function f over mt. For example, this function can be used to convert a match-tree of position information to a tree of strings. The function is applied to the tree in pre-order.
val app : ('a -> unit) -> 'a match_tree -> unit: app f mt applies the given function to the nodes in the tree in pre-order.
val foldl : ('a * 'b -> 'b) -> 'b -> 'a match_tree -> 'b: foldl f init mt folds the function f over mt in left-to-right pre-order using init as the initial value.
val foldr : ('a * 'b -> 'b) -> 'b -> 'a match_tree -> 'b: foldr f init mt folds the function f over mt in right-to-left post-order using init as the initial value.
val find : ('a -> bool) -> 'a match_tree -> 'a option: find pred mt returns SOME info where info is the first information that satisfies pred in a pre-order traversal of the tree. It returns NONE if there is no match information that satisfies pred.
val num : 'a match_tree -> int: num mt returns the number of sub-matches in the tree; i.e., the number of nodes not counting the root.

Synopsis

Interface

Description

See Also