diff options
Diffstat (limited to 'prolog/problems')
-rw-r--r-- | prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/en.py | 71 | ||||
-rw-r--r-- | prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py | 7 |
2 files changed, 73 insertions, 5 deletions
diff --git a/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/en.py b/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/en.py index 7e7a7d3..601488a 100644 --- a/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/en.py +++ b/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/en.py @@ -1,9 +1,10 @@ name = 'evenlen/1 + oddlen/1' -slug = 'check if the length of a list is even or odd' +slug = 'check if the length of a list is even or odd (without arithmetics)' description = '''\ <p><code>evenlen(L)</code>: the list <code>L</code> has an even number of elements.<br /> <code>oddlen(L)</code>: the list <code>L</code> has an odd number of elements.</p> +<p>Don't use arithmetic operations with this exercise, it destroys the point of it!</p> <pre> ?- oddlen([1,2,3,4,5]). true. @@ -13,4 +14,70 @@ description = '''\ true. </pre>''' -hint = {} +plan = ['''\ +<p>You can solve this exercise as two separate, albeit similar, ones, or as a single exercise that +intertwines two predicates. The second option is probably more interesting.</p> +''', '''\ +<p>Intertwining in this case means that one predicate calls the other and vice versa. Even. Odd. Even. Odd.</p> +''', '''\ +<p>If the tail (list without a single head) is of <em>even</em> length, then the whole list is of +<em>odd</em> length. And vice versa.</p> +'''] + +hint = { + 'eq_instead_of_equ': '''\ +<p>The operator <code>==</code> is "stricter" than operator <code>=</code> in the sense that +for the latter it is enough to be able to make the two operands equal (unification). Perhaps by using <code>=</code> +you can make the predicates <code>oddlen/1</code> and <code>evenlen/1</code> more general +(e.g. able to work with output arguments becoming inputs).</p> +<p>Of course, you can also solve the exercise without explicit use of either of these two operators, just +remember that unification is implicitly performed with the predicate's arguments (head of clause).</p> +''', + + 'eq_instead_of_equ_markup': '''\ +<p>Perhaps the operator for unification (=) would be better?</p> +''', + + 'base_case': '''\ +<p>Did you think of a base case? What's the simplest case that you can trivially solve?</p> +''', + + 'extra_base_case': '''\ +<p>You're getting duplicate solutions. It's enough to only have a single base case for this pair of +predicates; you don't need one for <code>evenlen/1</code> and one for <code>oddlen/1</code>.</p> +''', + + 'arbitrary_base_case': '''\ +<p>It seems that you accept an arbitrary result (a variable without an assigned value). This will not be ok.</p> +<p>Note that <code>_</code> is not the same as <code>[_]</code>. The first pattern represents an arbitrary +variable (anything), the second a list with <em>a single</em> arbitrary element.</p> +''', + + 'arithmetics_used': '''\ +<p>Please don't use arithmetics to solve this exercise, not even for counting the length of the list. +It can be solved without that and it's also a much nicer idea or two.</p> +''', + +'odd_and_even_mixed_up': '''\ +<p>Did you mix up odd and even? Zero is even, one is odd, two is... ;)</p> +''', + + 'recursive_case': '''\ +<p>The base case is ok. However, what about the general recursive case?</p> +''', + + 'predicate_always_false': '''\ +<p>It seems your predicate is <emph>always</emph> "false". Did you give it the correct name, +or is it perhaps misspelled?</p> +<p>If the name is correct, check whether something else is misspelled, perhaps there is a full stop instead of +a comma or vice versa, or maybe you typed a variable name in lowercase?</p> +<p>It is, of course, also possible that your conditions are too restrictive, or even impossible to satisfy +(as would be, for example, the condition that <code>N</code> is equal to <code>N + 1</code>, +or something similarly impossible).</p> +''', + + 'timeout': '''\ +<p>Is there an infinite recursion at work here? How will it ever stop?</p> +<p>Or perhaps is there a missing, faulty, or simply incompatible (with the general recursive case) base case?</p> +''', +} diff --git a/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py b/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py index 000ce1a..1c0b596 100644 --- a/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py +++ b/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py @@ -4,6 +4,7 @@ slug = 'Brez aritmetike preveri, če je seznam sode ali lihe dolžine' description = '''\ <p><code>evenlen(L)</code>: seznam <code>L</code> ima sodo število elementov.<br /> <code>oddlen(L)</code>: seznam <code>L</code> ima liho število elementov.</p> +<p>Ne uporabljaj aritmetike pri tej nalogi, ker to uniči njeno poanto!</p> <pre> ?- oddlen([1,2,3,4,5]). true. @@ -19,15 +20,15 @@ Druga verzija je verjetno bolj zanimiva.</p> ''', '''\ <p>Prepletanje tu pomeni, da ena naloga kliče drugo in obratno. Sodo. Liho. Sodo. Liho.</p> ''', '''\ -<p>Če je rep (seznam brez ene glave) <em>sode</em> dolžine, potem je celoten seznam </em>lihe</em> dolžine. +<p>Če je rep (seznam brez ene glave) <em>sode</em> dolžine, potem je celoten seznam <em>lihe</em> dolžine. In obratno.</p> '''] hint = { 'eq_instead_of_equ': '''\ <p>Operator <code>==</code> je strožji od operatorja <code>=</code> v smislu, da je za slednjega dovolj, -da elementa lahko naredi enaka (unifikacija). Morda z uporabo <code>=</code> narediš predikat -<code>memb/2</code> delujoč tudi v kakšni drugi smeri.</p> +da elementa lahko naredi enaka (unifikacija). Morda z uporabo <code>=</code> narediš predikata +<code>oddlen/1</code> in <code>evenlen/1</code> delujoča tudi v kakšni drugi smeri.</p> <p>Seveda pa lahko nalogo rešiš brez obeh omenjenih operatorjev, spomni se, da lahko unifikacijo narediš implicitno že kar v argumentih predikata (glavi stavka).</p> ''', |