Code editing in Comma

The Comma editor works largely like other graphical text editors. Those who are used to working in Vim may find the IdeaVim plugin useful. One may install it through the Plugins section of the Settings dialog.


Ctrl+F searches within the current file, while Ctrl+Shift+F can perform a text search over the whole project.

Similarly, Ctrl+R does a textual replace within the current file, the Ctrl+Shift+R provides this across the entire project.

AST-based selection

Pressing Ctrl+W will select the current program element. Pressing it again will expand the selection to the next program element. Ctrl+Shift+W will make the selection narrower again.

AST selection example

This is especially useful for selecting valid program elements to copy/paste, but also can come in handy to check the precedence of a complex expression!

Comment code out

Ctrl+/ will comment out the current line, or selected lines, of code - unless that line is already commented out, in which case it will uncomment it.

Smart enter

Pressing Ctrl+Shift+Enter will complete the current statement “smartly”. For example, pressing it after typing class SomeName will insert the curly braces and place the cursor inside of the class body. Similar happens with routine declarations and control flow statements. On other statements, it inserts a ; and then places the cursor onto the next line.

Smart enter demo

Duplicate or cut a line

Press Ctrl+D to duplicate the current line, and Ctrl+X to cut the current line.

Move statement up/down

Alt+Shift+Up and Alt+Shift+Down can be used to move the current line up and down. But what if you need to move a multi-line statement? Ctrl+Shift+Up and Ctrl+Shift+Down move statements up and down, correctly handling multi-line ones.

Move statement demo

Code folding

Use Ctrl+Num pad - to collapse the code at the current location, and Ctrl+Num pad + to expand it again.

Mark all references

When the cursor is on a symbol, for example a variable, then all usages of that variable currently on the screen will be shown with a gently colored background. But how to know if there are usages off screen too? Ctrl+Shift+F7 highlights them more vividly, and also shows the locations of other usages on the scroll bar. Press Ctrl+Shift+F7 on that symbol again to clear this.