~mdw / fringe / blame
| Commit | Line | Data |
|---|---|---|
| 2bd37ef1 MW |
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 -------------------------------------------------- |