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Metaprogramming: Difference between revisions
→{{header|Common Lisp}}: Show identity comprehension too. Anyone care for state transformer?
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Also, a monad is a class, and there is a way in the DEFINE-MONAD syntax to declare what the base classes are (multiple inheritance) as well as any additional custom slots.
Another example, using the identity monad. With the identity monad, the comprehension becomes a sequence of successive variable bindings, and a form evaluated in the scope of those bindings. It is basically like a "Lispified" Haskell DO syntax:
<lang lisp>(identity-comp (list x y z) (x 1) (y (* 3 x)) (z (+ x y)))
-> (1 3 4)
</lang>
I.e. combine the values X, Y and Z into a triplet list, were X is 1, Y is 3X, and Z is X + Y.
To see the original version of this code with lengthy comments, have a look in the Lisp Pastebin. http://paste.lisp.org/display/71196
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