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Polymorphic copy: Difference between revisions
Added EchoLisp
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See also: [[Deepcopy#E]]
=={{header|EchoLisp}}==
<lang scheme>
(lib 'types)
(lib 'struct)
(struct T (integer:x)) ;; super class
(struct S T (integer:y)) ;; sub class
(struct K (T:box)) ;; container class, box must be of type T, or derived
(define k-source (K (S 33 42)))
(define k-copy (copy k-source))
k-source
→ #<K> (#<S> (33 42)) ;; new container, with a S in box
k-copy
→ #<K> (#<S> (33 42)) ;; copied S type
(set-S-y! (K-box k-source) 666) ;; modify k-source.box.y
k-source
→ #<K> (#<S> (33 666)) ;; modified
k-copy
→ #<K> (#<S> (33 42)) ;; unmodified
(K "string-inside") ;; trying to put a string in the container box
😡 error: T : type-check failure : string-inside → 'K:box'
</lang>
=={{header|F_Sharp|F#}}==
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