huffman code lisp prolog

implement huffman libraries lisp prolog imht-decode bits huffman-tree message ht-encode message huffman-tree bits ht-encode-file filename huffman-tree bits ht-generate-huffman-tree symbols-n-weights huffman-tree ht-generate-symbol-bits-table huffman-tree symbol-bits-table ht-pprint-huffman-tree huffman-tree &optional (indent-level 0) huffman-tree is a Huffman tree (its root); symbols-n-weigths is a list of pairs of symbol-weight (<symbol>. <weight>); symbol-bits-table is a list of pairs (<symbol>. <bits>). The ht-encode-file function reads a text from a file and then invokes ht-encode on the read. Functions must generate errors (with the function error) if encoding and / or decoding are not possible. The ht-print-huffman-tree function prints a Huffman Tree terminal and serves essentially for debugging. No perticular format is required, but printed information has to be fine represent the tree structure of Huffman Prolog You must implement the following predicates: ht_decode / 3 Bits HuffmanTree Message ht_encode / 3 Message HuffmanTree Bits ht_encode_file / 3 Filename HuffmanTree Bits ht_generate_huffman_tree / 2 SymbolsAndWeights HuffmanTree ht_generate_symbol_bits_table / 2 HuffmanTree SymbolBitsTable ht_pprint_huffman_tree / 1 HuffmanTree The constraints are the same as above (obviously remodeled in Prolog). In particular, Symbolic pairs and bits symbol are represented as pairs lists of two elements (i.e., (<symbol>, <weight>) and (<symbol>, <bits>)). Predicates must fail if there are errors or if they encode and / or decoding can not be completed. The predicate ht_print_huffman_tree prints a Huffman Tree terminal. Examples The most important example to keep in mind (the specification, according to a more correct terminology) is the following. In Common Lisp: cl-prompt> (defparameter ht (ht-generate-huffman-tree '<symbols-n-weights>)) HT cl-prompt> (defparameter message '<some-message>) MESSAGE cl-prompt> (equal message (ht-decode (ht-encode message ht ht)) T In Prolog: ? - assert (symbols_n_weights (<symbols-n-weights>)). Yes. ? - assert (message (<some-message>)). Yes. ?- symbol_n_weights(SWs), | message(M), | ht_generate_huffman_tree(SWs, HT), | ht_encode(M, HT, Bits), | ht_decode(Bits, HT, M). Yes. As you may have noticed, the structure of the implementation of a tree has not been specified Huffman. A problem you will have will be in managing ordered sets of elements (leaves and tree nodes in construction); you will need to implement a structure and / or functions that keep them together ordered. The implementation of the various functions and predicates is relatively simple once it is exploited the sorting of knots and leaves. If you find yourself writing features or long predicates or complex then you are probably on the wrong track..