View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000325 | 1003.1(2008)/Issue 7 | Shell and Utilities | public | 2010-09-29 15:09 | 2013-04-16 13:06 |
| Reporter | eblake | Assigned To | ajosey | ||
| Priority | normal | Severity | Objection | Type | Omission |
| Status | Closed | Resolution | Accepted As Marked | ||
| Name | Eric Blake | ||||
| Organization | Red Hat | ||||
| User Reference | ebb.tr | ||||
| Section | tr | ||||
| Page Number | 3247 | ||||
| Line Number | 108366 | ||||
| Interp Status | --- | ||||
| Final Accepted Text | 0000325:0000575 | ||||
| Summary | 0000325: tr and m4 translit behavior when string1 has repeated characters | ||||
| Description | The description for sed's y operator is explicit that repeating characters in the first argument of a transliteration operation has unspecified results: "if any of the characters in string1 appear more than once, the results are undefined." (line 105011) However, there is no corresponding text for either tr or m4's translit built-in. And while sed leaves the behavior unspecified, existing implementation practice for both tr and m4 is consistent across a large set of implementations. Oddly enough, though, the two programs historically have a different interpretation: tr favors the last instance of a character in string1, while m4 favors the first: $ echo a | tr aa 01 1 $ echo 'translit(a,aa,01)' | m4 0 The proposal below gives two alternatives; I would prefer the first which mandates existing practice, but it may be deemed worth using the second proposal to be more conservative and mirror sed's wording. Meanwhile, 'tr -s a' falls into the category of -d not being specified, but since it does not have a string2 argument, the text of line 108366 is not applicable. Both options in the proposal fix the wording to make this clear. The wording for m4 assumes the resolution for 0000242 has been applied first. This proposal does not change the wording for sed, but it appears that most sed implementations match the tr behavior of favoring the last instance of a character. | ||||
| Desired Action | Option 1: At line 108366 (XCU tr EXTENDED DESCRIPTION), change: Each input character found in the array specified by string1 shall be replaced by the character in the same relative position in the array specified by string2. to: If string2 is present, each input character found in the array specified by string1 shall be replaced by the character in the same relative position in the array specified by string2. If a character occurs more than once in string1, the replacement shall be from the final position of that character. At line 94344 (XCU m4 EXTENDED DESCRIPTION translit), change: The defining text of the translit macro shall be the first argument with every character that occurs in the second argument replaced with the corresponding character from the third argument. If no replacement character is specified for some source character because the second argument is longer than the third argument, that character shall be deleted from the first argument in translit's defining text. to: The defining text of the translit macro shall be the first argument with every character that occurs in the second argument replaced with the corresponding character from the third argument. If a character appears more than once in the second argument, the replacement shall correspond to the first instance of the character. If no replacement character is specified for the first instance of a source character because the second argument is longer than the third argument, that character shall be deleted from the first argument in translit's defining text. Option 2: At line 108366 (XCU tr EXTENDED DESCRIPTION), change: Each input character found in the array specified by string1 shall be replaced by the character in the same relative position in the array specified by string2. When the array specified by string2 is shorter that the one specified by string1, the results are unspecified. to: If string2 is present, each input character found in the array specified by string1 shall be replaced by the character in the same relative position in the array specified by string2. If the array specified by string2 is shorter that the one specified by string1, or if a character occurs more than once in string1, the results are unspecified. After line 94349 (XCU m4 EXTENDED DESCRIPTION translit), add another sentence: The behavior is unspecified if the same character appears more than once in the second argument. | ||||
| Tags | tc1-2008 | ||||
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The WG will be applying Option #2 from the Desired Action field; this will both clarify that this behavior is indeed undefined in the specification and also clean up the text for tr in this case. |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2010-09-29 15:09 | eblake | New Issue | |
| 2010-09-29 15:09 | eblake | Status | New => Under Review |
| 2010-09-29 15:09 | eblake | Assigned To | => ajosey |
| 2010-09-29 15:09 | eblake | Name | => Eric Blake |
| 2010-09-29 15:09 | eblake | Organization | => Red Hat |
| 2010-09-29 15:09 | eblake | User Reference | => ebb.tr |
| 2010-09-29 15:09 | eblake | Section | => tr |
| 2010-09-29 15:09 | eblake | Page Number | => 3247 |
| 2010-09-29 15:09 | eblake | Line Number | => 108366 |
| 2010-09-29 15:09 | eblake | Interp Status | => --- |
| 2010-10-14 15:44 | msbrown | Note Added: 0000575 | |
| 2010-10-14 15:44 | msbrown | Resolution | Open => Accepted As Marked |
| 2010-10-14 15:46 | msbrown | Final Accepted Text | => 0000325:0000575 |
| 2010-10-14 15:46 | msbrown | Tag Attached: tc1-2008 | |
| 2010-10-14 15:56 | geoffclare | Status | Under Review => Resolved |
| 2013-04-16 13:06 | ajosey | Status | Resolved => Closed |
