koans, stuff
dice - more practice with signal and clog backquote - first practice with @,a splicing macros - some news of common errors: - capturing outer symbols, so caller expects them to be used, but invisible internal values take their place - evaluating "pass by name" forms too many times - evaluating them in surprising order
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efim
@@ -23,19 +23,22 @@
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(cond ((null forms) 'nil)
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((null (rest forms)) (first forms))
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(t `(when ,(first forms)
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,(generate (rest forms)))))))
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,(generate (rest forms))))))) ; wowy
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(generate forms)))
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(when (= 2 3) "hello")
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(define-test my-and
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;; ASSERT-EXPANDS macroexpands the first form once and checks if it is equal
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;; to the second form.
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(assert-expands (my-and (= 0 (random 6)) (error "Bang!"))
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'(when (= 0 (random 6)) (error "Bang!")))
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;; ASSERT-EXPANDS macroexpands the first form once and checks if it is equal
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;; to the second form.
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(assert-expands (my-and (= 0 (random 6)) (error "Bang!"))
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'(when (= 0 (random 6)) (error "Bang!")))
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(assert-expands (my-and (= 0 (random 6))
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(= 0 (random 6))
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(= 0 (random 6))
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(error "Bang!"))
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____))
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'(when (= 0 (random 6))
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(when (= 0 (random 6)) (when (= 0 (random 6)) (error "Bang!"))))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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@@ -43,16 +46,19 @@
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(define-test variable-capture
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(macrolet ((for ((var start stop) &body body)
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`(do ((,var ,start (1+ ,var))
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(limit ,stop))
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((> ,var limit))
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,@body)))
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`(do ((,var ,start (1+ ,var))
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(limit ,stop))
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((> ,var limit))
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,@body)))
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(let ((limit 10)
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(result '()))
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(for (i 0 3)
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(push i result)
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(assert-equal ____ limit))
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(assert-equal ____ (nreverse result)))))
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(push i result)
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(assert-equal 3 limit))
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(assert-equal '(0 1 2 3) (nreverse result))))) ; didn't get it on first tries, ugh
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;; oh, ok - then try to use names that wouldn't happen in outside condext
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;; so that explicitly defined things in outside context get overshadowed
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;; ok
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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@@ -60,20 +66,23 @@
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;;; meant to be evaluated once.
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(define-test multiple-evaluation
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;; We use MACROLET for defining a local macro.
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(macrolet ((for ((var start stop) &body body)
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`(do ((,var ,start (1+ ,var)))
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((> ,var ,stop))
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,@body)))
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(let ((side-effects '())
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(result '()))
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;; Our functions RETURN-0 and RETURN-3 have side effects.
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(flet ((return-0 () (push 0 side-effects) 0)
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(return-3 () (push 3 side-effects) 3))
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(for (i (return-0) (return-3))
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(push i result)))
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(assert-equal ____ (nreverse result))
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(assert-equal ____ (nreverse side-effects)))))
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;; We use MACROLET for defining a local macro.
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(macrolet ((for ((var start stop) &body body)
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`(do ((,var ,start (1+ ,var)))
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((> ,var ,stop))
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,@body)))
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(let ((side-effects '())
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(result '()))
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;; Our functions RETURN-0 and RETURN-3 have side effects.
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(flet ((return-0 () (push 0 side-effects) 0)
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(return-3 () (push 3 side-effects) 3))
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(for (i (return-0) (return-3))
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(push i result)))
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(assert-equal '(0 1 2 3) (nreverse result))
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(assert-equal '(0 3 3 3 3 3) (nreverse side-effects)))))
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; omg, fuck this guessing
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; ok, the ,stop was evaluated on each iteraction
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; to check "whether to stop"
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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@@ -81,36 +90,53 @@
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;;; subforms.
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(define-test wrong-evaluation-order
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(macrolet ((for ((var start stop) &body body)
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;; The function GENSYM creates GENerated SYMbols, guaranteed to
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;; be unique in the whole Lisp system. Because of that, they
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;; cannot capture other symbols, preventing variable capture.
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(let ((limit (gensym "LIMIT")))
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`(do ((,limit ,stop)
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(,var ,start (1+ ,var)))
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((> ,var ,limit))
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,@body))))
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(let ((side-effects '())
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(result '()))
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(flet ((return-0 () (push 0 side-effects) 0)
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(return-3 () (push 3 side-effects) 3))
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(for (i (return-0) (return-3))
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(push i result)))
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(assert-equal ____ (nreverse result))
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(assert-equal ____ (nreverse side-effects)))))
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(macrolet ((for ((var start stop) &body body)
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;; The function GENSYM creates GENerated SYMbols, guaranteed to
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;; be unique in the whole Lisp system. Because of that, they
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;; cannot capture other symbols, preventing variable capture.
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(let ((limit (gensym "LIMIT")))
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`(do ((,limit ,stop)
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(,var ,start (1+ ,var)))
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((> ,var ,limit))
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,@body))))
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(let ((side-effects '())
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(result '()))
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(flet ((return-0 () (push 0 side-effects) 0)
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(return-3 () (push 3 side-effects) 3))
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(for (i (return-0) (return-3))
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(push i result)))
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(assert-equal '(0 1 2 3) (nreverse result))
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(assert-equal '(3 0) (nreverse side-effects)))))
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;; didn't got on first try,
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;; but yes, for gensym limit ,stop is evaluated first
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define-test for
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(macrolet ((for ((var start stop) &body body)
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;; Fill in the blank with a correct FOR macroexpansion that is
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;; not affected by the three macro pitfalls mentioned above.
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____))
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(let ((side-effects '())
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(result '()))
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(flet ((return-0 () (push 0 side-effects) 0)
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(return-3 () (push 3 side-effects) 3))
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(for (i (return-0) (return-3))
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(push i result)))
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(assert-equal '(0 1 2 3) (nreverse result))
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(assert-equal '(0 3) (nreverse side-effects)))))
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(macrolet ((for ((var start stop) &body body)
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;; Fill in the blank with a correct FOR macroexpansion that is
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;; not affected by the three macro pitfalls mentioned above.
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(let ((initial (gensym "INITIAL"))
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(limit (gensym "LIMIT")))
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`(do* ((,initial ,start)
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(,limit ,stop)
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(,var ,initial (1+ ,var)))
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((> ,var ,limit))
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,@body))))
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(let ((side-effects '())
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(result '()))
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(flet ((return-0 () (push 0 side-effects) 0)
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(return-3 () (push 3 side-effects) 3))
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(for (i (return-0) (return-3))
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(push i result)))
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(assert-equal '(0 1 2 3) (nreverse result))
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(assert-equal '(0 3) (nreverse side-effects)))))
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;; (do* ((a (return-0))
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;; (b (return-3))
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;; (i a (1+ i)))
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;; ((> i b))
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;; (push i result))
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;;
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;; so, my mistake was: using DO and trying to cross reference temp vars
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;; and mistyping 1+ as 1_
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