lfex / los Goto Github PK

> (include-lib "los/include/multi-methods.lfe")
> (defmulti area 'type)
> (defmethod area 'rectangle
       ((`(#(length ,l) #(width ,w)))
         (* l w)))
> (area '(#(type triangle) #(base 2) #(height 4)))
  4.0

(defmodule polymorph
  (export all))

(defun area
  ((`(,type . ,rest))
   (dispatch 'area type rest)))

(defun dispatch
  ((fname `#(type ,type) args)
   (call (MODULE) (list_to_atom (++ (atom_to_list fname)
                                    "-"
                                    (atom_to_list type))) args)))

(defun area-triangle
  ((`(#(base ,b) #(height ,h)))
   (* b h (/ 1 2))))

(defun area-rectangle
  ((`(#(length ,l) #(width ,w)))
   (* l w)))

(c "examples/no-macros/polymorph.lfe")
#(module polymorph)
(slurp "examples/no-macros/polymorph.lfe")
#(module polymorph)
> (area '(#(type triangle) #(base 2) #(height 4)))
4.0
> (area '(#(type rectangle) #(length 2) #(width 4)))
8

(defun area-square
  ((`(#(side ,s)))
   (* s s)))

(defun area-circle
  ((`(#(radius ,r)))
   (* (math:pi) r r)))

> (area '(#(type square) #(side 2)))
  4
> (area '(#(type circle) #(radius 2)))
  12.566370614359172