Enum FileAnchor 

pub enum FileAnchor {
    End,
    Start,
    Line(u32),
}

Where in a target file an Effect::WriteToFile lands.

Examples

use lattice_grammar::effect::FileAnchor;

// A 3-line file: append inserts before line 3 (one past the last).
assert_eq!(FileAnchor::End.resolve_line(3), 3);
assert_eq!(FileAnchor::Start.resolve_line(3), 0);
assert_eq!(FileAnchor::Line(1).resolve_line(3), 1);
// Past the end clamps to append instead of failing.
assert_eq!(FileAnchor::Line(9).resolve_line(3), 3);

A position, not a range, and the asymmetry with Effect::ApplyEdit is the answer rather than an inconsistency to tidy away (cross-file-writes.md §4).

For its own buffer a producer holds a document handle: it can read lines, count them, and compute a range that means something. For another file it holds nothing — it has never seen the bytes, so a range it invented would be a guess. These are the three positions namable without reading, and they are exactly the three archive, refile and capture need.

Insert-only also bounds the blast radius: it cannot silently destroy content in a file the user was not looking at, where a range-carrying primitive could on an off-by-one and the user would find out later.

Variants

End

After the last line — the common case. Archive, refile and capture all append by default.

Start

Before the first line.

Line(u32)

Before this 0-based line. Past the end clamps to FileAnchor::End rather than erroring: a producer computing a line from a file it has not read can legitimately be off, and refusing to file the text at all is worse than filing it at the end.

Implementations

impl FileAnchor

pub fn resolve_line(self, line_count: u32) -> u32

The 0-based line an insert should happen before, given the target’s line count.

line_count is the number of content lines. End yields line_count, i.e. one past the last — which is what “append” means to the caller building a Position.

Trait Implementations

impl Clone for FileAnchor

fn clone(&self) -> FileAnchor

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for FileAnchor

impl Debug for FileAnchor

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for FileAnchor

impl PartialEq for FileAnchor

fn eq(&self, other: &FileAnchor) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for FileAnchor