zl:1 - FTP

179 zl :displace
zl:displace form expansion Function
Replaces the car and cdr of form so that it looks like:
(s i : d i sp 1 aced original-form expansion)
form must be a list. original-form is equal to form but has a different toplevel
cons so that the replacing mentioned above does not affect it.
si:displaced is a macro, which returns the caddr of its own macro form.
So when the si:displaced form is given to the evaluator, it "expands" to expansion.
z1:displace returns expansion.
zl:dlet ((variable-pattern value-pattern) ... ) body... Special Form
Binds variables to values, using de struc turing, and evaluates the body
forms in the context of those bindings. In place of a variable to be assigned,
you can provide a tree of variables. The value to be assigned must
be a tree of the same shape. The trees are destructured into their component
parts, and each variable is assigned to the corresponding part of the
value tree.
First the value-patterns are evaluated. If a variable-pattern is a symbol, it
is bound to the result of eValuating the corresponding value-pattern. If
variable-pattern is a tree, the result of evaluating value-pattern should be a
tree of the same shape. The trees are de structured, and each variable that
is a component of variable-pattern is bound to the value that is the corresponding
element of the tree that results from evaluating value-pattern.
The bindings happen in parallel; all the value-patterns are evaluated before
any variables are bound. Finally, the body forms are evaluated sequentially,
the old values of the variables are restored, and the result of the last
body form is returned. Example:
(2l:dlet (((a b) '((x y) 2))
(c 'd))
(values a b c))
I
returns (x y), z, and d.
z1:dlet* ((variable-pattern value-pattern) ... ) body... Special Form
Binds variables to values, using de structuring, and evaluates the body
forms in the context of those bindings. In place of a variable to be assigned,
you can provide a tree of variables. The value to be assigned must
be a tree of the same shape. The trees are destructured into their component
parts, and each variable is assigned to the corresponding part of the
value tree.
The first value-pattern is evaluated. If variable-pattern is a symbol, it is
bound to the result of evaluating value-pattern. If variable-pattern is a tree,
the result of evaluating value-pattern should be a tree of the same shape.
The trees are destructured, and each variable that is a component of