5 ms·

It's opt-in, otherwise most packages would break. To enable it per-file use a file-local variable: ;;; -*- lexical-binding: t -*-

• perlgeek 14y ago
  How ironic. Wouldn't it make much sense to enable it per lexical scope? Or as Perl did it (18 years ago) with a new keyword, so that you can use both dynamic and lexical variables in the same file? Best of both worlds.
  • m00natic 14y ago
    Well, there has been lexical-let in the cl package for quite a while.
  • onedognight 14y ago
    You can use both in the same file; you just need to declare the dynamic ones using defvar, etc. If you turn lexical-binding on blindly, the compiler will usually tell you which variables you need to mark as dynamic.
  • unhammer 14y ago
    (eval form t) enables lexical scoping for form. http://yoo2080.wordpress.com/2011/12/31/lexical-scoping-and-dynamic-scoping-in-emacs-lisp/ http://yoo2080.wordpress.com/2011/12/31/lexical-scoping-and-... is highly recommended reading btw.
  • rcthompson 14y ago
    It has to be this way to remain backward-compatible. Similar to the issues Perl is going through with things like enabling strict by default (you have to request at least a certain version, I think 5.12), and distinguishing a Perl 6 file from Perl 5 one.