if-let (bindings &body (then-form &optional else-form))
Creates new variable bindings, and conditionally executes either then-form or else-form. else-form defaults to nil.
bindings must be either single binding of the form:
(variable initial-form)or a list of bindings of the form:
((variable-1 initial-form-1) (variable-2 initial-form-2) ... (variable-n initial-form-n))All initial-forms are executed sequentially in the specified order. Then all the variables are bound to the corresponding values.
If all variables were bound to true values, the then-form is executed with the bindings in effect, otherwise the else-form is executed with the bindings in effect.