binding.lisp - clic - Clic is an command line interactive client for gopher written in Common LISP
 (HTM) git clone git://bitreich.org/clic/ git://enlrupgkhuxnvlhsf6lc3fziv5h2hhfrinws65d7roiv6bfj7d652fid.onion/clic/
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       binding.lisp (2959B)
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            1 (in-package :alexandria)
            2 
            3 (defmacro if-let (bindings &body (then-form &optional else-form))
            4     "Creates new variable bindings, and conditionally executes either
            5 THEN-FORM or ELSE-FORM. ELSE-FORM defaults to NIL.
            6 
            7 BINDINGS must be either single binding of the form:
            8 
            9  (variable initial-form)
           10 
           11 or a list of bindings of the form:
           12 
           13  ((variable-1 initial-form-1)
           14   (variable-2 initial-form-2)
           15   ...
           16   (variable-n initial-form-n))
           17 
           18 All initial-forms are executed sequentially in the specified order. Then all
           19 the variables are bound to the corresponding values.
           20 
           21 If all variables were bound to true values, the THEN-FORM is executed with the
           22 bindings in effect, otherwise the ELSE-FORM is executed with the bindings in
           23 effect."
           24     (let* ((binding-list (if (and (consp bindings) (symbolp (car bindings)))
           25                              (list bindings)
           26                              bindings))
           27          (variables (mapcar #'car binding-list)))
           28     `(let ,binding-list
           29        (if (and ,@variables)
           30            ,then-form
           31            ,else-form))))
           32 
           33 (defmacro when-let (bindings &body forms)
           34     "Creates new variable bindings, and conditionally executes FORMS.
           35 
           36 BINDINGS must be either single binding of the form:
           37 
           38  (variable initial-form)
           39 
           40 or a list of bindings of the form:
           41 
           42  ((variable-1 initial-form-1)
           43   (variable-2 initial-form-2)
           44   ...
           45   (variable-n initial-form-n))
           46 
           47 All initial-forms are executed sequentially in the specified order. Then all
           48 the variables are bound to the corresponding values.
           49 
           50 If all variables were bound to true values, then FORMS are executed as an
           51 implicit PROGN."
           52   (let* ((binding-list (if (and (consp bindings) (symbolp (car bindings)))
           53                            (list bindings)
           54                            bindings))
           55          (variables (mapcar #'car binding-list)))
           56     `(let ,binding-list
           57        (when (and ,@variables)
           58          ,@forms))))
           59 
           60 (defmacro when-let* (bindings &body body)
           61   "Creates new variable bindings, and conditionally executes BODY.
           62 
           63 BINDINGS must be either single binding of the form:
           64 
           65  (variable initial-form)
           66 
           67 or a list of bindings of the form:
           68 
           69  ((variable-1 initial-form-1)
           70   (variable-2 initial-form-2)
           71   ...
           72   (variable-n initial-form-n))
           73 
           74 Each INITIAL-FORM is executed in turn, and the variable bound to the
           75 corresponding value. INITIAL-FORM expressions can refer to variables
           76 previously bound by the WHEN-LET*.
           77 
           78 Execution of WHEN-LET* stops immediately if any INITIAL-FORM evaluates to NIL.
           79 If all INITIAL-FORMs evaluate to true, then BODY is executed as an implicit
           80 PROGN."
           81   (let ((binding-list (if (and (consp bindings) (symbolp (car bindings)))
           82                           (list bindings)
           83                           bindings)))
           84     (labels ((bind (bindings body)
           85                (if bindings
           86                    `(let (,(car bindings))
           87                       (when ,(caar bindings)
           88                         ,(bind (cdr bindings) body)))
           89                    `(progn ,@body))))
           90       (bind binding-list body))))