42 lines
1.1 KiB
Clojure
42 lines
1.1 KiB
Clojure
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(defmacro hello [x]
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(str "Hello, " x))
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(defmacro infix [form]
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(list (second form) (first form) (nth form 2)))
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(defmacro infix-better [form]
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`(~(second form) ; Note the syntax-quote (`) and unquote (~) characters!
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__
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__ ))
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(defmacro r-infix [form]
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(cond (not (seq? form))
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__
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(= 1 (count form))
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`(r-infix ~(first form))
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:else
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(let [operator (second form)
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first-arg (first form)
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others __]
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`(~operator
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(r-infix ~first-arg)
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(r-infix ~others)))))
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; "Macros are like functions created at compile time"
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(= __ (hello "Macros!"))
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; "I can haz infix?"
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(= __ (infix (9 + 1)))
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; "Remember, these are nothing but code transformations"
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(= __ (macroexpand '(infix (9 + 1))))
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; "You can do better than that - hand crafting FTW!"
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(= __ (macroexpand '(infix-better (10 * 2))))
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; "Things don't always work as you would like them to... "
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(= __ (macroexpand '(infix-better ( 10 + (2 * 3)))))
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; "Really, you don't understand recursion until you understand recursion"
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(= 36 (r-infix (10 + (2 * 3) + (4 * 5))))
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