CODEWITHSUNDEEP
lispelisp
shelper
shelper

Reputation: 10573

lexical binding for a predefined global variable

Here is the snippet that confuses me:

(setq lexical-binding t)
(defvar x 0)
    
(setq test (let ((x 1))
            (lambda () 
               x)))

(funcall test)

My understanding is that since lexical-binding is true, then the x of value 1 should cover the scope of let, which should include the x in the definition of lambda, as such, the test should return value of 1 instead of 0, but it turns out to return 0, which is the value of x by defvar.

Did I misunderstand anything?

UPDATE Just for clarification, I would like to put my understanding here. Dynamical bounding means it only have one symbol and the value is popped in and out in a stack. As such, when the definition of lambda is done, the value used in let is popped out. lexical/static bounding means the value is always been checked in the context of the lexical environment, so as long there is let before lambda definition, the value in let is used. variable defined by defvar is always dynamically bound, as such, lexical-binding control here does not make any difference.

Upvotes: 3

Views: 174

Answers (1)

Travis
Travis

Reputation: 435

According to https://www.gnu.org/software/emacs/manual/html_node/elisp/Using-Lexical-Binding.html, even when lexical-binding is non-nil, special variables (like x since it was defined with defvar) are still dynamically bound.

Upvotes: 3

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