Hello [EMAIL PROTECTED]!
On 08-Gen-00, you wrote:
w> 1. Can you simulate a static local variable in REBOL? The
There are plenty of ways to do this...
>> use [static] [
[ static: none
[ f: func [a] [
[ print ["Last was:" static]
[ static: a
[ ]
[ ]
>> f 1
Last was: none
== 1
>> f 5
Last was: 1
== 5
>> f "But..."
Last was: 5
== "But..."
>> recycle
>> f "... there's still the bug!"
** CRASH (Should not happen) - Corrupt datatype: 66
Just another one:
>> f: func [a] [
[ static: [none]
[ print ["Last was:" static/1]
[ change/only static a
[ ]
>> f 1
Last was: none
== []
>> f 4
Last was: 1
== []
>> f "This should work always, I hope..."
Last was: 4
== []
>> f ":-)"
Last was: This should work always, I hope...
== []
w> 2. Can you create a line of REBOL code, including two or
w> more functions of arity one or more (that take one or more
w> parameters), that results in the same result forwards or
w> backwards? To verify, put the code in a block, and try:
Well, this way's too simple. :-) I could write:
>> f: func [:a :b] ["Result"]
>> code: [f f f]
== [f f f]
>> do code
== "Result"
>> do head reverse code
== "Result"
It's better to exclude these simple cases from the puzzle, to make
it more interesting... :-)
w> 3. Can you make a function which takes one argument, unless
w> called with a refinement in which case the function takes no
w> arguments?
This one's challenging, at least at first sight. One solution
might be:
>> f: func [
[ [catch]
[ a [any-type!]
[ /b
[ ] [
[ either b [
[ "No parameter!"
[ ] [
[ if not value? 'a [throw make error! [script no-arg f a]]
[ "One parameter"
[ ]
[ ]
>> f
** Script Error: f is missing its a argument.
** Where: f
>> f 2
== "One parameter"
>> f 4
== "One parameter"
>> f/b
== "No parameter!"
But:
>> f/b 4
== "No parameter!"
Hmm... I'll have to think about this... :-)
w> 4. Can you create a parse rule that recognizes whether a
w> string of numbers is from the Fibonacci sequence?
Generalizing for any sequence,
>> sequence: [13 46 38 59 79 47 22 4 68 2]
== [13 46 38 59 79 47 22 4 68 2]
>> string: " 13 46 38 59 79 47 22 4 68 2"
== " 13 46 38 59 79 47 22 4 68 2"
>> parse string [
[ (i: 1 number: form sequence/1)
[ some [
[ number (i: i + 1 number: form pick sequence i)
[ ]
[ ]
== true
You can apply the same kind of rule for any function...
Regards,
Gabriele.
--
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| Gabriele Santilli / /_/_\_\ \ Amiga Group Italia --- L'Aquila |
| GIESSE on IRC \ \-\_/-/ / http://www.amyresource.it/AGI/ |
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