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The Parts of a  let Expression

A  let expression is a list of three parts. The first part is the symbol  let . The second part is a list, called a varlist, each element of which is either a symbol by itself or a two-element list, the first element of which is a symbol. The third part of the  let expression is the body of the  let . The body usually consists of one or more lists.

A template for a  let expression looks like this:

(let varlist body@dots{})
The symbols in the varlist are the variables that are given initial values by the  let special form. Symbols by themselves are given the initial value of  nil ; and each symbol that is the first element of a two-element list is bound to the value that is returned when the Lisp interpreter evaluates the second element.

Thus, a varlist might look like this:  (thread (needles 3)) . In this case, in a  let expression, Emacs binds the symbol  thread to an initial value of  nil , and binds the symbol  needles to an initial value of 3.

When you write a  let expression, what you do is put the appropriate expressions in the slots of the  let expression template.

If the varlist is composed of two-element lists, as is often the case, the template for the  let expression looks like this:

(let ((variable value)
      (variable value)
      @dots{})
      body@dots{})

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