There is a constraint for inclusive range check (aka closed set check): Assert.That(..., Is.InRange(a, b)). I wonder if there is a built in Assert for open set check? I want to test if a value is between two others exclusive.
No, it only has the closed range check. For an exclusive check, you will have to spell out the comparison explicitly.
For example...
Assert.That(myVal, Is.GreaterThan(4).And.LessThan(10));
Related
I found the discussion at https://groups.google.com/forum/#!topic/orient-database/Y0QJiXk7d1I to be very useful to help me set up a strict schema with edges in it. This is my code
val fileLink = schema.createClass(DefinedInS.label, g.getEdgeBaseType())
fileLink.setStrictMode(true)
fileLink.createProperty("out", OType.LINK, fqnSymbol).setNotNull(true)
fileLink.createProperty("in", OType.LINK, fileCheck).setNotNull(true)
fqnSymbol.createProperty("out_" + DefinedInS.label, OType.LINKBAG).setNotNull(true)
fileCheck.createProperty("in_" + DefinedInS.label, OType.LINKBAG).setNotNull(true)
but I am confused why I need the last two lines at all, aren't they redundant (or at least implied by the fileLink properties?). Could somebody please explain why they are needed?
In addition, for this example I want exactly one link from a fqnSymbol to a fileCheck but this seems to required that LINKBAG is used (it fails if I use LINK). Is that something I should be allowed to do?
Futhermore, is there any performance benefit to be gained from adding an index on the edge? My usecase is such that I will always have a fqnSymbol at hand when I want to lookup a fileCheck.
I raised https://github.com/orientechnologies/orientdb/issues/5494 to request better documentation in this area.
When one creates an edge (that is, an instance of E), the points of connection are stored at both endpoints (the vertices):
(vertex) -> [edge] -> (vertex)
It's my understanding that if the edge is an immediate instance of E, then those endpoints are properties named out_ and in_. (Similarly, if they are immediate instances of some subclass, say EE, of E, then they would be named out_EE and in_EE.) Often these details don't matter (e.g. outE() collects all outgoing edges), but sometimes they do (as when defining constraints on properties).
Regarding the multiplicity constraint:
I want exactly one link from a fqnSymbol to a fileCheck ...
This constraint can be enforced (at least to a degree) using MIN and MAX:
alter property fqnSymbol.out_ MIN 1;
alter property fqnSymbol.out_ MAX 1;
(Fortunately, the MIN and MAX constraints won't prevent an fqnSymbol vertex from being created in the first place :-)
Tighter enforcement may require writing hooks or triggers.
Suppose one needs to select the real solutions after solving some equation.
Is this the correct and optimal way to do it, or is there a better one?
restart;
mu := 3.986*10^5; T:= 8*60*60:
eq := T = 2*Pi*sqrt(a^3/mu):
sol := solve(eq,a);
select(x->type(x,'realcons'),[sol]);
I could not find real as type. So I used realcons. At first I did this:
select(x->not(type(x,'complex')),[sol]);
which did not work, since in Maple 5 is considered complex! So ended up with no solutions.
type(5,'complex');
(* true *)
Also I could not find an isreal() type of function. (unless I missed one)
Is there a better way to do this that one should use?
update:
To answer the comment below about 5 not supposed to be complex in maple.
restart;
type(5,complex);
true
type(5,'complex');
true
interface(version);
Standard Worksheet Interface, Maple 18.00, Windows 7, February
From help
The type(x, complex) function returns true if x is an expression of the form
a + I b, where a (if present) and b (if present) are finite and of type realcons.
Your solutions sol are all of type complex(numeric). You can select only the real ones with type,numeric, ie.
restart;
mu := 3.986*10^5: T:= 8*60*60:
eq := T = 2*Pi*sqrt(a^3/mu):
sol := solve(eq,a);
20307.39319, -10153.69659 + 17586.71839 I, -10153.69659 - 17586.71839 I
select( type, [sol], numeric );
[20307.39319]
By using the multiple argument calling form of the select command we here can avoid using a custom operator as the first argument. You won't notice it for your small example, but it should be more efficient to do so. Other commands such as map perform similarly, to avoid having to make an additional function call for each individual test.
The types numeric and complex(numeric) cover real and complex integers, rationals, and floats.
The types realcons and complex(realcons) includes the previous, but also allow for an application of evalf done during the test. So Int(sin(x),x=1..3) and Pi and sqrt(2) are all of type realcons since following an application of evalf they become floats of type numeric.
The above is about types. There are also properties to consider. Types are properties, but not necessarily vice versa. There is a real property, but no real type. The is command can test for a property, and while it is often used for mixed numeric-symbolic tests under assumptions (on the symbols) it can also be used in tests like yours.
select( is, [sol], real );
[20307.39319]
It is less efficient to use is for your example. If you know that you have a collection of (possibly non-real) floats then type,numeric should be an efficient test.
And, just to muddy the waters... there is a type nonreal.
remove( type, [sol], nonreal );
[20307.39319]
The one possibility is to restrict the domain before the calculation takes place.
Here is an explanation on the Maplesoft website regarding restricting the domain:
4 Basic Computation
UPD: Basically, according to this and that, 5 is NOT considered complex in Maple, so there might be some bug/error/mistake (try checking what may be wrong there).
For instance, try putting complex without quotes.
Your way seems very logical according to this.
UPD2: According to the Maplesoft Website, all the type checks are done with type() function, so there is rather no isreal() function.
At my company we've recently been working on a modification to an existing program that used the following logic to perform some database field assignments:
db-buffer1.field1 = if db-buffer1.field1 <> db-buffer2.field2
then db-buffer2.field2
else db-buffer1.field1
I'm not 100% sure of the original programmer's intention here. Can anyone help me understand the value in comparing whether or not the field values are different before deciding whether to assign the new field?
If the comparison is 'false' and we end up assigning db-buffer1.field1 = db-buffer1.field1 do we avoid a write operation on the database?
Also note that this example is part of a larger ASSIGN statement that contains several fields running similar assignment/comparison logic. Does that have any effect on the value of this additional code? (i.e. Do all comparisons in the ASSIGN statement have to succeed in order to avoid a DB write?)
An "IF function" on the right hand side of an expression is a lot like a "ternary operator" in C or Javascript (the "?:" construct).
It only impacts the portion of the ASSIGN that it is part of. When I write code using those I always encase it in parens to make it clear. Like so:
assign
a = ( if x = y then b else c )
z = 2
.
Whether or not a WRITE happens depends a lot on the rest of the code.
Judging only by this snippet you are going to write SOMETHING (at least logically). db-buffer.field1 is going to get a value assigned to it regardless. The IF logic on the right-hand side is just picking if it will be field1 or field2. In the case that boils down to field1 = field1 you might hope that some lower layer will optimize the write out of existence. I don't see your Progress version posted but if it is v9 or better then it may very well be optimized away. (Prior to v9 it would not have been.)
If you really want to "avoid the write" at the application level you should code it like this:
if field1 <> field2 then
assign
field1 = field2
.
This form does not use the IF function, it is just a normal IF ... THEN statement. It is much clearer and it does not depend on optimizations at a lower level. Of course the snippet shown is said to be part of a larger ASSIGN -- so it may or may not be sensible to break it out and write it as I've shown. But it would be worth thinking about.
It appears that the programmer is checking if field1 is not equal to field2 go ahead and update it.
They might as well simply use the following since either way the field is being assigned:
assign db-buffer1.field1 = db-buffer2.field2.
When using the ASSIGN statement (recommended always), from a logical perspective you have to keep in mind that each line is assigned separately.
Tom has a great answer here that gives more information regarding efficiency/history of the ASSIGN statement.
I would be very interested in seeing the rest of the assign statement, but I would also get rid of the if logic in this case as it adds no value, just and extra instruction. As Terry stated above
ASSIGN db-buffer1.field1 = db-buffer2.field2.
I am tutoring someone in basic search and sorts. In insertion sort I iterate negatively when I have a value that is greater than the one previous to it in numerical terms. Now of course this approach can cause issues because there is a check which calls for array[-1] which does not exist.
As underlined in bold below, adding the and x > 0 boolean prevents the index issue.
My question is how is this the case? Wouldn't the call for array[-1] still be made to ensure the validity of both booleans?
the_list = [10,2,4,3,5,7,8,9,6]
for x in range(1,len(the_list)):
value = the_list[x]
while value < the_list[x-1] **and x > 0**:
the_list[x] = the_list[x-1]
x=x-1
the_list[x] = value
print the_list
I'm not sure I completely understand the question, and I don't know what programming language this is, but most modern programming languages use so-called short-circuit Boolean evaluation by default so that the logical expression isn't evaluated further once the outcome is known.
You can use that to guard against range overflow, like this:
while x > 0 and value < the_list[x-1]
but the check of x's range here must come before the use.
AND operation returns true if and only if both arguments are true, so if one of arguments is false there's no point of checking others as the final value is already known at that point. As for your example, usually evaluation goes from left to right but it is not a principle and it looks the language you used is not following that rule (othewise it still should crash on array lookup). But ut may be, this particular implementation optimizes this somehow (which IMHO is not good idea) and evaluates "simpler" things first (like checking if x > 0) before it look up the array. check the specs why this exact order works for you as in most popular languages you would still crash if test x > 0 wouldn't be evaluated before lookup
How to check if the given value is a number in Prolog without using built-in predicates like number?
Let's say I have a list [a, 1, 2, 3]. I need a way to check if every element within this list is a number. The only part of the problem that bothers me is how to do the check itself without using the number predicate.
The reason why I'm trying to figure this out is that I've got a college assignment where it's specifically said not to use any of the built-in predicates.
You need some built-in predicate to solve this problem - unless you enumerate all numbers explicitly (which is not practical since there are infinitely many of them).
1
The most straight-forward would be:
maplist(number, L).
Or, recursively
allnumbers([]).
allnumbers([N|Ns]) :-
number(N),
allnumbers(Ns).
2
In a comment you say that "the value is given as an atom". That could mean that you get either [a, '1', '2'] or '[a, 1, 2]`. I assume the first. Here again, you need a built-in predicate to analyze the name. Relying on ISO-Prolog's errors we write:
numberatom(Atom) :-
atom_chars(Atom, Chs),
catch(number_chars(_, Chs), error(syntax_error(_),_), false).
Use numberatom/1 in place of number/1, So write a recurse rule or use maplist/2
3
You might want to write a grammar instead of the catch... goal. There have been many such definitions recently, you may look at this question.
4
If the entire "value" is given as an atom, you will need again atom_chars/2or you might want some implementation specific solution like atom_to_term/3 and then apply one of the solutions above.