Use zprint to format a range of lines in a file

Usually, zprint is used to format all of the lines in a file.

However, you can format a range of lines in a file using either the command line zprint programs, or when using zprint as a library.

A range specification looks like:

{:input {:range {:start start-line-number :end end-line-number}}}

where start-line-number and end-line-number are zero based, and are inclusive (that is to say, both lines will be formatted).

Since zprint can only format effectively if it knows the left margin, the start-line-number and end-line-number are adjusted (usually expanded outwards) to encompass one or more top level expressions.

The expression in which the start-line-number is located is determined, and then the start-line-number is moved up to the first non-blank line beyond the previous expression. This is in order to encompass any ;!zprint {} directives that might appear directly before the expression. The expression in which the end-line-number is located is determined, and the end-line-number is moved down to the last line of that expression.

The specifics of how the line numbers are handled are: the start-line-number is moved to the first non-blank line after the previous expression, where comments are considered non-blank lines. If there is no previous expression the start-line-number is set to the beginning of the file. The end-line-number is moved to the last line of the expression in which the end-line-number falls. If the end-line-number does not fall inside an expression, it is moved up to the first previous non-blank line. The range will never start or end on a blank line inside of a file.

If the start-line-number is negative, it is considered to be before the start of the file. If the end-line-number is negative, nothing will be formatted in the file. If the end-line-number is before the start-line-number, it will be set to the start-line-number A start-line-number beyond the end of the file will cause nothing to be included in the range, while an end-line-number beyond the end of the file will simply represent that the end of the range should be the end of the file.

If both start-line-number and end-line-number are within the same gap between expressions, nothing will be formatted.

Note that any ;!zprint directives that appear before the previous expression will not be recognized when formatting a range of lines.

Note also that zprint will not leave trailing spaces on a line, but this is only true for lines that are part of the range -- the other lines are untouched.

If any problems occur when trying to determine the current or previous expressions (since a quick parse of the entire file is required for this to happen), the entire file is formatted.