gtk-editable-delete-text (editable &key start-pos end-pos)

editable -- a gtk-editable widget
start -- an integer with the start position
end -- an integer with the end position

Deletes a sequence of characters. The characters that are deleted are those characters at positions from start up to, but not including end. If end is negative, then the characters deleted are those from start to the end of the text.

Note that the positions are specified in characters, not bytes.