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Closed 9 years ago.
I just heard something very insteresting but cannot find any ressources.
The story is that when faced with an algorithmic problem that requiered multiple ifs, one student of a friend did answer with a mathematic one liner.
Now I already knew that you could do anyting with math but I want to be able to do it.
From what I know it might be possible to do a loop given the shape of those function, but conditions?
Does someone know how to resolve something like:
IF boolean
THEN expression
ELSE expression2
in math terms (without Bool algebra)?
Best regards,
Sarfraz
Assuming boolean is either 0 or 1, and expressions are mathematical:
expr = boolean * expression + (1-boolean) * expression2
Provided that boolean is 0 or 1:
result = boolean*expression+(1-boolean)*expression2
Are you referring to a multiplexer?
If the boolean is S, expression is A and expression2 is B, then the formula for result Z is
Related
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Closed 10 years ago.
How puts variable in iterators code Ruby
EX: (1,2,3).select { |v| puts v > 2}
Seems syntax error, I think you want something like this
[1,2,3].select { |v| puts v > 2 }
output would be :
false
false
true
Take a look here
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Closed 10 years ago.
In scheme I have to use random to define a procedure that accepts no arguments and returns an integer in the range 1 to 10, inclusive and i cant use if. im lost =(
If your Scheme provides a random function, you want either
(define (1-10-rand)
(+ 1 (random 10)))
or
(define (1-10-rand)
(floor (* 10 (random))))
depending on whether you have (random n) --> integer in [0, n-1]) or (random) -> float in [0,1]
Be advised that this isn't standards-compliant. For absolute portability, write your own RNG.
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Closed 10 years ago.
I want to convert the expression ((A + B) * C – (D – E) ^ (F + G)) to equivalent Prefix and Postfix notations. What answers do you get?
Well, there are many steps. Since the question does not reflet your evolution so far, I'll just give you some hints
Define the operations taken in account
Give them a priority
Define what an expression is
What should you do when an expression has parenthesis and when its not
This should get you on track
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Closed 10 years ago.
I wish to define a predicate powerset(X, P) which is true when P is the powerset of X. Should work whether or not P is ground.
Since you use SICStus Prolog you can use the subseq0(+Sequence, ?SubSequence) from library(lists), which "is true when SubSequence is a subsequence of Sequence, but may be Sequence itself" (Quoting from the manual http://www.sics.se/sicstus/docs/4.0.2/html/sicstus/lib_002dlists.html).
?- setof(X, subseq0([a,b,c],X), Xs).
Xs = [[],[a],[a,b],[a,b,c],[a,c],[b],[b,c],[c]]
If you are not allowed to use library predicates you can implement the subseteq0 as explained in gnu Prolog powerset modification, which I quote here for the sake of completeness (with thanks to gusbro)
powerset([], []).
powerset([H|T], P) :- powerset(T,P).
powerset([H|T], [H|P]) :- powerset(T,P).
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
I need to write SCC algorithm in standard ML. But I don't know how.
I have following TYPEs which have to be uesd in the code:
type vertex = int
type edge = int * int
type graph = (vertex * vertex list) list
fun dfs (g: graph) (n: vertex): vertex list =
let
fun helper (todo: vertex list) (visited: vertex list): vertex list =
case todo of
[] => []
| h::t => if (List.exists (fn x => x = h) visited)
then helper t visited
else
let
val adj = case List.find (fn (n, _) => n = h) g of
NONE => raise Fail "incomplete adjacency list"
| SOME (_, adj) => adj
in
h :: (helper (adj # t) (h::visited))
end
in
helper [n] []
end
The above code has been compiled and run correctly.
I put these in the code because I know in computing SCC dfs is needed.
Does anyone have a solution?
Pseudo code - http://algowiki.net/wiki/index.php/Tarjan's_algorithm.
I'm guessing that you're trying to use Standard ML ( http://www.smlnj.org/sml.html ) .
During your classroom time, your teacher should have presented either a modelling tool with which to create your SML code, or should have referred you to a resource with which to write the code. S/he should also have presented sample code - and your book (or a CD in the back of your book) should include SML code.
Assuming you don't have a modelling tool, my recommendation is as follows. Start by refering to the sample code that your teacher or book offers, and pick the code that solves a problem most similar to your needs. Copy & paste that into your answer, being absolutely sure to clearly cite the source at the very beginning of the answer. Then, use other examples from class, the details from your book, and the resources under the "documentation and literature" section of smlnj.org (particularly the tutorials) to implement your solution.
Then, if you have a stumbling block - something that wasn't discussed in class, and wasn't covered in your book, but you just can't solve, you should discuss it with your TA or your teacher. If you ask the question to one of them, then your teacher can find out that the topic wasn't clearly covered in class. If you don't ask them, then they won't know, and much of the rest of your class may have difficulty with the topic.
And finally, if your teacher and TA aren't available, and you're running into a problem that you just don't know how to solve, and you have a very specific question (like, "here's my code; it won't compile and I can't figure out why"), at that point you should ask Stack Overflow.