| paul@6 | 1 | #!/usr/bin/env python |
| paul@6 | 2 | |
| paul@6 | 3 | """ |
| paul@6 | 4 | Sequence operations. |
| paul@6 | 5 | |
| paul@6 | 6 | Copyright (C) 2015 Paul Boddie <paul@boddie.org.uk> |
| paul@6 | 7 | |
| paul@6 | 8 | This program is free software; you can redistribute it and/or modify it under |
| paul@6 | 9 | the terms of the GNU General Public License as published by the Free Software |
| paul@6 | 10 | Foundation; either version 3 of the License, or (at your option) any later |
| paul@6 | 11 | version. |
| paul@6 | 12 | |
| paul@6 | 13 | This program is distributed in the hope that it will be useful, but WITHOUT |
| paul@6 | 14 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS |
| paul@6 | 15 | FOR A PARTICULAR PURPOSE. See the GNU General Public License for more |
| paul@6 | 16 | details. |
| paul@6 | 17 | |
| paul@6 | 18 | You should have received a copy of the GNU General Public License along with |
| paul@6 | 19 | this program. If not, see <http://www.gnu.org/licenses/>. |
| paul@6 | 20 | """ |
| paul@6 | 21 | |
| paul@6 | 22 | from native import _isinstance |
| paul@6 | 23 | |
| paul@6 | 24 | def _getitem(seq, index): |
| paul@6 | 25 | |
| paul@6 | 26 | "Return the item or slice specified by 'index'." |
| paul@6 | 27 | |
| paul@6 | 28 | if _isinstance(index, int): |
| paul@6 | 29 | index = _normalise_index(index, seq.__len__()) |
| paul@6 | 30 | return seq.__get_single_item__(index) |
| paul@6 | 31 | elif _isinstance(index, slice): |
| paul@6 | 32 | return seq.__getslice__(index.start, index.end) |
| paul@6 | 33 | else: |
| paul@6 | 34 | raise TypeError |
| paul@6 | 35 | |
| paul@6 | 36 | def _getslice(seq, start, end=None): |
| paul@6 | 37 | |
| paul@6 | 38 | "Return a slice starting from 'start', with the optional 'end'." |
| paul@6 | 39 | |
| paul@6 | 40 | length = seq.__len__() |
| paul@6 | 41 | |
| paul@6 | 42 | if start is None: |
| paul@6 | 43 | start = 0 |
| paul@6 | 44 | else: |
| paul@6 | 45 | start = _normalise_index(start, length) |
| paul@6 | 46 | |
| paul@6 | 47 | if end is None: |
| paul@6 | 48 | end = length |
| paul@6 | 49 | else: |
| paul@6 | 50 | end = _normalise_index(end, length) |
| paul@6 | 51 | |
| paul@6 | 52 | result = [] |
| paul@6 | 53 | while start < end: |
| paul@6 | 54 | result.append(seq.__get_single_item__(start)) |
| paul@6 | 55 | start += 1 |
| paul@6 | 56 | return result |
| paul@6 | 57 | |
| paul@6 | 58 | def _get_absolute_index(index, length): |
| paul@6 | 59 | |
| paul@6 | 60 | """ |
| paul@6 | 61 | Return the absolute index for 'index' given a collection having the |
| paul@6 | 62 | specified 'length'. |
| paul@6 | 63 | """ |
| paul@6 | 64 | |
| paul@6 | 65 | if index < 0: |
| paul@6 | 66 | return length + index |
| paul@6 | 67 | else: |
| paul@6 | 68 | return index |
| paul@6 | 69 | |
| paul@6 | 70 | def _normalise_index(index, length): |
| paul@6 | 71 | |
| paul@6 | 72 | "Normalise 'index' for a collection having the specified 'length'." |
| paul@6 | 73 | |
| paul@6 | 74 | return _min(length, _max(0, _get_absolute_index(index, length))) |
| paul@6 | 75 | |
| paul@6 | 76 | def _max(x, y): |
| paul@6 | 77 | |
| paul@6 | 78 | "Return the maximum of 'x' and 'y'." |
| paul@6 | 79 | |
| paul@6 | 80 | if x >= y: |
| paul@6 | 81 | return x |
| paul@6 | 82 | else: |
| paul@6 | 83 | return y |
| paul@6 | 84 | |
| paul@6 | 85 | def _min(x, y): |
| paul@6 | 86 | |
| paul@6 | 87 | "Return the minimum of 'x' and 'y'." |
| paul@6 | 88 | |
| paul@6 | 89 | if x <= y: |
| paul@6 | 90 | return x |
| paul@6 | 91 | else: |
| paul@6 | 92 | return y |
| paul@6 | 93 | |
| paul@6 | 94 | def _tuple(l): pass |
| paul@6 | 95 | |
| paul@6 | 96 | # vim: tabstop=4 expandtab shiftwidth=4 |
