| 1 | ### -*-icon-*- |
| 2 | ### |
| 3 | ### An Icon implementation of a `same-fringe' solver. |
| 4 | |
| 5 | ###-------------------------------------------------------------------------- |
| 6 | ### Utilities. |
| 7 | |
| 8 | procedure bail(msg) |
| 9 | ## Report MSG as an error, and quit. |
| 10 | |
| 11 | write(&errout, &progname, ": ", msg) |
| 12 | flush(&errout) |
| 13 | exit(1) |
| 14 | end |
| 15 | |
| 16 | procedure same_sequence_p(test, aseq, bseq) |
| 17 | ## Succeed if the sequences generated by coexpressions ASEQ and BSEQ equal, |
| 18 | ## in the sense that TEST succeeds when applied to corresponding elements, |
| 19 | ## and the sequences have the same length. |
| 20 | |
| 21 | local a, b |
| 22 | |
| 23 | while a := @aseq do |
| 24 | if not (b := @bseq) | not test(a, b) then fail |
| 25 | if @bseq then fail |
| 26 | return |
| 27 | end |
| 28 | |
| 29 | procedure print_sequence(aseq) |
| 30 | ## Write the elements of the sequence generated by coexpression ASEQ |
| 31 | ## followed by a newline. |
| 32 | |
| 33 | every writes(|@aseq) |
| 34 | write() |
| 35 | end |
| 36 | |
| 37 | procedure string_equal_p(a, b) |
| 38 | ## Succeed if strings A and B are equal. Useful as a TEST for |
| 39 | ## `print_sequence'. |
| 40 | |
| 41 | return a == b |
| 42 | end |
| 43 | |
| 44 | ###-------------------------------------------------------------------------- |
| 45 | ### Node structure. |
| 46 | |
| 47 | record node(left, data, right) |
| 48 | ## A simple binary tree structure. |
| 49 | |
| 50 | procedure fringe(node) |
| 51 | ## Generate the elements of the tree headed by NODE inorder. |
| 52 | |
| 53 | if /node then fail |
| 54 | suspend fringe(node.left) | node.data | fringe(node.right) |
| 55 | end |
| 56 | |
| 57 | procedure scan_tree() |
| 58 | ## Scan a tree from the current subject, advancing the position over it. |
| 59 | ## See `parse_tree' for the syntax. |
| 60 | |
| 61 | local data, left, right |
| 62 | |
| 63 | if ="(" then { |
| 64 | left := scan_tree() |
| 65 | data := move(1) | bail("no data") |
| 66 | right := scan_tree() |
| 67 | =")" | bail("missing )") |
| 68 | return node(left, data, right) |
| 69 | } else |
| 70 | return &null |
| 71 | end |
| 72 | |
| 73 | procedure parse_tree(string) |
| 74 | ## Parse a tree from STRING and return its root. |
| 75 | ## |
| 76 | ## The syntax is as follows. |
| 77 | ## |
| 78 | ## tree ::= empty | `(' tree char tree `)' |
| 79 | ## |
| 80 | ## Ambiguity is resolved by treating a `(' as starting a tree when a tree |
| 81 | ## is expected. |
| 82 | |
| 83 | local t |
| 84 | |
| 85 | return string ? { |
| 86 | t := scan_tree() |
| 87 | if not pos(0) then bail("trailing junk") |
| 88 | t |
| 89 | } |
| 90 | end |
| 91 | |
| 92 | ###-------------------------------------------------------------------------- |
| 93 | ### Main program. |
| 94 | |
| 95 | procedure main(argv) |
| 96 | local trees |
| 97 | |
| 98 | if *argv = 1 then |
| 99 | print_sequence(create fringe(parse_tree(argv[1]))) |
| 100 | else if *argv = 2 then |
| 101 | if same_sequence_p(string_equal_p, |
| 102 | create fringe(parse_tree(argv[1])), |
| 103 | create fringe(parse_tree(argv[2]))) then |
| 104 | write("match") |
| 105 | else |
| 106 | write("no match") |
| 107 | else |
| 108 | bail("bad args") |
| 109 | end |
| 110 | |
| 111 | ###----- That's all, folks -------------------------------------------------- |