Parkour ¶

2.1 Objects ¶

Parkour maps the typical objects used in text editors to S-expressions (atoms and lists):

• word — atom, or, when the cursor is exactly on a delimiter, list or quasi-list¹
• block — parenthesized list
• sentence — the current list or quasi-list
• paragraph — the current top-level expression
• section/page — form-feed²-separated group of top-level expressions

2.2 Motions ¶

Parkour provides the following motion types:

• Structured motions — move either horizontally (without leaving the current list or quasi-list), or diagonally (ascend or descend) through the tree of nested expressions.

  When the cursor is in code, they skip over comments. (For other ways to descend into comments, see word-descent, delete-descent, semicolon-descent)

  When the cursor is inside a quasi-list, horizontal motions land on individual words.
  Moreover, when in a group of line comments, horizontal motions will leave the current comment and enter the previous/next one, effectively treating the whole group as a single comment.

• Word motions — always land on atoms/words. They float up or sink down in the tree hierarchy, and enter or leave strings/comments, as needed.

2.3 Electricity/DWIM ¶

Besides the sexp-aware editing operators, which have dedicated key bindings, Parkour enhances the behaviour of common keys like BS, DEL, RET, SPC, and ;.

• RET
  • at end of line — opens an empty indented line after the current one
  • at start of line — opens an empty indented line before the current one
  • before closing paren — opens an empty indented line after the last list element
  • on empty indented line — does nothing (only one empty line is allowed in a list, and it will be collapsed on the next reindent)
  • in line comment — splits the comment
  • elsewhere in code — puts the text to the right of the cursor on a new indented line
• BS
  • after a closing delimiter — moves the cursor to the left of it
  • after an opening delimiter — does nothing
  • at start of line — joins it with the previous line (and cleans up any leftovers of indentation)
  • same, but after a line comment — does nothing (to prevent accidentally commenting out the current line)
  • at start of line comment — joins it with the previous one
  • in empty line comment — same, unless the empty comment is the last in a group. In that case, it splices the comment (which deletes it, effectively).
• DEL
  • before an opening delimiter — moves the cursor to the right of it
  • before a closing delimiter — does nothing
  • at end of line — joins it with the next line (and cleans up any leftovers of indentation)
  • at start of line — does nothing (indentation cannot be manually influenced)
  • before a line comment — moves the cursor past the opening semicolons
  • at end of line comment — joins it with the next one
  • in empty line comment — same, unless the empty comment is the last in a group. In that case, it splices the comment (which deletes it, effectively).
• SPC
  • on empty indented line — deletes it and inserts the space on the previous line
  • between a space and another character — does nothing (only one space is allowed between same-line expressions)
• ;
  • at start of line — inserts two or three semicolons (inside a list, or at top level, respectively), and a space.
    If the line was originally empty, the cursor ends up inside the new comment, so you can start typing.
    If there was code on the line, the cursor is kept before the semicolons, so you can move away from the commented out code without having to ascend out of it first.
  • before a line comment — moves the cursor past the opening semicolons
  • elsewhere in code — shifts anything to the right of the cursor to column 40 and inserts a single semicolon

  If in the code that would be commented out there was a delimiter whose match is on another line, the delimiter and anything to the right of it is moved to the next line in order to prevent any unbalancing.

2.4 Paren autocorrect ¶

In Clojure and Fennel square brackets are required at certain places. Parkour will insert a square bracket even if you pressed the wrong kind of delimiter (paren, brace, or even double-quote).

In some Scheme dialects (e.g., Racket) square brackets are recommended for readability reasons. If you are using such a dialect, you can get this behaviour by enabling the auto_square_brackets option.

3.1 Editor-specific features ¶

Some features could not be abstracted into the Parkour library and had to be implemented in the top-layer code of a particular editor plugin.