Proposal for regions

Michael, Jim and I worked out a proposal for regions on the phone last Friday. It incorporates Luke’s concern that endColumn wasn’t previously defined consistently (Issue #171).

 

Here’s what I pasted into Issue #93, “Problems with regions”. I’m going to start writing the spec-ese for this and I’ll move it’s adoption at TC #18 on May 30th.

FYI @michaelcfanning @kupsch @lukecartey

Here is the outcome of our discussion on Friday 5/18. I include a couple of points that we didn't state explicitly, but that I think are obvious (like #3).

1.     Column ranges are half-open: they exclude the column specified by endColumn.

2.     If endLine is missing, it defaults to startLine.

3.     There is no default value for startLine.

EXAMPLE: The region startLine = 12, startColumn = 3, endColumn = 6 consists of the three characters in columns 3 through 5 of line 12.

4.     If startColumn is missing, it defaults to 1.

EXAMPLE: The region startLine = 12, endColumn = 6 consists of the five characters in columns 1 through 5 of line 12.

5.     If endColumn is missing, it defaults to the number of characters on the last line of the region (excluding the newline sequence).

EXAMPLE: Suppose line 12 consists of the characters "abcd\r\n" (the four characters "abcd" followed by the two-character newline sequence "\r\n"). Then the region startLine = 12, startColumn = 2 consists of the three characters "bcd".

6.     As a result of #4 and #5, a region specified solely by startLine consists of the entire line, excluding the newline sequence.

EXAMPLE: Suppose line 12 consists of the characters "abcd\r\n". Then the region startLine = 12 consists of the four characters "abcd".

7.     To specify an insertion point, explicitly specify both startColumn and endColumn, on the same line, with equal values.

EXAMPLE: The region startLine = 12, startColumn = 5, endColumn = 5 specifies an insertion point before column 5 on line 12.

EXAMPLE: The region startLine = 12, startColumn = 1, endColumn = 1 specifies an insertion point at the beginning of line 12.

NOTE: Omitting endColumn does not specify an insertion point (endColumn does not default to startColumn, contrary to the current spec).

8.     Line ranges are closed: they include the line specified by endLine.

9.     If a region contains more than one line, it includes the newline sequence for all but the last line.

EXAMPLE: The region startLine = 12, startColumn = 3, endLine = 14 includes columns 3 through the end of line 12 (including the newline sequence), all of line 13 (including the newline sequence), and all of line 14 except for the newline sequence.

EXAMPLE: The region startLine = 12, endLine = 14 includes all of lines 12 through 14 except for the newline sequence on line 14.

EXAMPLE: The region startLine = 12, endLine = 13, endColumn = 1 consists of all of line 12 (including the newline sequence). The "cursor position" is before column 1 on line 13.

 

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Thanks,

Larry