Add documentation

trees/cb/authors.txt

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+Michael Raitza

trees/cb/cb-docs.factor

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+USING: arrays assocs byte-arrays help.markup help.syntax io.encodings.utf8
+kernel math serialize trees.cb.private ;
+IN: trees.cb
+
+HELP: CBTREE{
+{ $syntax "CBTREE{ { key value }... }" }
+{ $values { "key" "a key" } { "value" "a value" } }
+{ $description "Literal syntax for a crit-bit tree." } ;
+
+HELP: <cb>
+{ $values { "tree" cb } }
+{ $description "Creates an empty crit-bit tree" } ;
+
+HELP: >cb
+{ $values { "assoc" assoc } { "tree" cb } }
+{ $description "Converts any " { $link assoc } " into a crit-bit tree. If the input assoc is a " { $link cb } ", the elements are cloned before insertion. The resulting tree is, then, identical to the input, as crit-bit trees are unique for any given content." } ;
+
+HELP: cb
+{ $class-description "This is the class for binary crit-bit trees (i.e. discriminating on a single critical bit)." } ;
+
+HELP: key>bytes*
+{ $values { "key" object } { "bytes" byte-array } }
+{ $description "Converts a key, which can be any " { $link object } ", into a " { $link byte-array } ". Standard methods convert strings into its " { $link utf8 } " byte sequences and " { $link float } " values into byte arrays representing machine-specific doubles. Integrals are converted into a byte sequence of at least machine word size in little endian byte order."
+$nl
+"All other objects are serialized using " { $link object>bytes } ". In the standard implementation, this maps " { $link f } " to the byte array " { $snippet "B{ 110 }" } print-element " and " { $link t } " to " { $snippet "B{ 116 }" } ", which is identical to the respective integers." } ;
+
+ARTICLE: "trees.cb" "Binary crit-bit trees"
+"The " { $vocab-link "trees.cb" } " vocabulary is a library for binary critical bit trees, a variant of PATRICIA tries. A crit-bit tree stores each element of a non-empty set of keys K in a leaf node. Each leaf node is attached to the tree of internal split nodes for bit strings x such that x0 and x1 are prefixes of (serialized byte arrays of) elements in K and ancestors of other bit strings higher up in the tree. Split nodes store the prefix compressed as two values, the byte number and bit position, in the subset of K at which the prefixes of all ancestors to the left differ from all ancestors to the right."
+$nl
+"Serialization on keys is implemented using " { $link key>bytes } ". Crit-bit trees can store arbitrary keys and values, even mixed. Due to the nature of crit-bit trees, for any given input set that shares a common prefix, the tree compresses the common prefix into the split node at the root extending the lookup by one for arbitrary long prefixes."
+$nl
+"Keys are serialized once for every lookup and insertion not adding a new leaf node. Two keys are serialized for every insertion adding a new leaf node to the tree."
+$nl
+"Due to ordering ancestors at split nodes into crit-bit '0' (left) and crit-bit '1' (right) the order of the elements in a crit-bit tree is total allowing efficient suffix searches and minimum searches."
+$nl
+"Crit-bit trees consume 2 * n - 1 nodes in total for storing n elements; each internal split node consumes two pointers and two fixnums; each leaf node two pointers to the key and value. Their shape is unique for any given set of keys, which also means lookup times are deterministic for a known set of keys regardless of insertion order or the tree having been cloned."
+$nl
+"Compared to hash tables, crit-bit trees provide fast access without being prone to malicious input (or a badly chosen hash function) and also provide ordered operations (e.g. finding minimums). Compared to heaps, they support exact searches and suffix searches in addition. Compared to other ordered trees (AVL, B-), they support the same set of operations while keeping a simpler inner structure."
+$nl
+"Crit-bit trees conform to the assoc protocol."
+;

trees/cb/summary.txt

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+Critical bit trees as described in http://cr.yp.to/critbit.html

trees/cb/tags.txt

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+collections