I am reading through the Julia manual right now and ran into my first potential disappointment.
I like being able to code conditional statements tersely. In R I might write:
if (x==y) print("Hello")
In Julia however I think I might need do
if x==y
println("Hello")
end
Or perhaps x==y ? print("Hello") : print("") which is certainly silly.
Is there some formulation in Julia for allowing for single line conditional statements?
You can write if x == y println("Hello") end or, as has become somewhat idiomatic, you can use the short-circuiting behavior of the && operator and write x == y && println("Hello"). In a very similar fashion it is fairly common to check some condition and throw an error if it isn't met by writing something like this: size(A) == size(B) || error("size mismatch").
Related
I used an || operator within the Kotlin IDEA but was throwing an error. This confused me, one of the first queries when searching google was a closed stack overflow thread with a snarky "answer" comment which wasn't helpful.
The first query in google hit is some function "or" gibberish.
My code:
if(inputAmount >= 0 || inputAmount = -99)
I understand what is "wrong". there was some logic errors the second part of the "if" statement should have been inputAmount == -99. In my case, the code needed to further be adjusted because of the actual type that was being used.
if(inputAmount >= 0.0 || inputAmount.toInt() == -99)
This appears to be different then other languages in that other languages just simply allow you to have your "logic" error with the "inputAmount = -99". So the '||' operator is allowed and is similar to most other languages.
So first step if encounter this error is to make sure your logic is correct. (check)
infix functions > sense according to the documentation "or" and "and" are infix functions that don't use the short circuit, is it technically wrong to call the "||" operator an "or" operator and should be called logical 'or'?
when referring to the infix 'or' how do people refer to that in Kotlin?
in boolean logic takes statements. A=b is a statement that is always true
No, it isn't. In C, C++ and Java it's an expression, and its value is the value of b. If b is false, it's false, if b is 10, it's 10. And you really don't want to confuse "statements" in programming languages with "statements" in logic; they are entirely different things.
Separately, C and C++ (but not Java) allow || to work on all integral types, and not just booleans (because they didn't originally have booleans as a separate type).
when referring to the infix function 'or' how do Kotlin folk typically refer to that?
Bitwise or for integral types, and I've never actually seen anyone use non-short-circuiting or on booleans, but if I had to I'd call it... well, non-short-circuiting or.
is it technically wrong to call the "||" operator an "or" operator and should be called logical 'or'
Both || and or (on booleans) are "logical 'or'" and I don't see any problem with calling them simply 'or'. If you need to distinguish use short-circuiting vs non-short-circuiting. But again, I've never actually ran into a use of the non-short-circuiting version.
I have this code:
IF (x>5 AND y=4) THEN
dbms_output.put_line("Y");
ELSE
dbms_output.put_line("N");
My question is: how do you change the code if you can not use AND as the operator but instead, you have to use OR to have the same logic and get the same result?
You can use DeMorgan's Law to rewrite it:
NOT (p AND q) == (NOT p) OR (NOT q)
So, in your case
IF (x>5 AND y=4) THEN "Y" ELSE "N"
IF (x<=5 OR y<>4) THEN "N" ELSE "Y"
Or and AND operator have completely different logic, you cannot use AND as the operator but instead, you have to use OR to have the same logic and get the same result.
If you change the line to read like this, it will work with only the OR operator:
IF (x<=5 OR y!=4) THEN dbms_output.put_line("N"); ELSE dbms_output.put_line("Y");=
The outcome is the same, but the logic is slightly different.
Is there a way in C/ObjectiveC
to shorten this?
if (a == b || a == c || a == d)
{
}
so that
i would have something like this?
if (a == (b || c || d))
{
}
I know the latter is not correct but what I want something that resembles plain english i.e.
If "a" equals this or this or this...then do something. I find repeating the ==
operator a bit redundant.
If you're working with objective-c objects:
if([#[b,c,d] containsObject:a])
Otherwise, there's no way to simplify your first implementation.
No, you've written it correctly the first time.
Incidentally, shorter code is not necessarily better code. It's often harder to read.
As the title says i was wondering if there is a way to use ternary operators with multiple statements in Objective C.
I know it can be easily done in some other languages like javascript, php, C etc but i couldn't find a solution for Objective C.
I want to implement something like this:
a > b ? ( statement1, statement2, statement3 ) : ( statement1, statement2 );
Basically i just want to avoid a lot of if-else blocks to maintain better code readability.
Please also suggest if using ternary operators instead of if-else blocks can harm app performance to a noticeable extent.
The Conditional operator ?: is not a replacement for an if/else block. I'm sure you could tweak the logic to make it work, but that would only obscure the meaning more.
My question is, "what are you saving?"
a > b ? ( statement1, statement2, statement3 ) : ( statement1, statement2 );
if (a > b) { statement1; statement2; statement3; } else { statement1; statement2; }
The if/else block is a grand total of 7 characters longer.
An even bigger question is, "Can the logic be composed in a better way?"
Look to see if the flow can be done differently with fewer ifs.
Look for places to create sub-routines.
You can easily do this; just be aware that the ternary operator can only include expressions, including comma expressions. So your statements can only be expressions, assignments, method calls etc. but no if / return / while and so on. And the ternary operator wants a result, so the last expressions in each group must have the same type; you can just add (void) 0 at the end of each list.
That said, you are most definitely not making your code more readable. Everyone reading it will start swearing at you and doubt your mental sanity. So don't do it.
The solution for your question (#user3752049) is:
a > b ? ^{ statement1; statement2; statement3;}() : ^{statement1; statement2;}();
Thanks
Currently, I'm using && and || instead of AND and OR because that's how I was taught. In most languages, however, both are valid syntax. Are there any advantages to one or the other in any language?
I did try to search for this question, but it's a bit hard. It doesn't interpret my input correctly.
You ask “Are there any advantages to one or the other in any language?” This is, of course, dependent on the programming language.
Languages that implement both and and && (and correspondingly or and ||) will do it one of two ways:
Both behave exactly the same way. In which case, there is no advantage provided by the language in using one over the other.
Each behaves differently. In which case, the advantage is that you can get different behaviour by using one or the other.
That all sounds a bit facetious, but it's really as specific as one can get without talking about a specific language. Your question explicitly wants to know about all languages, but it's a question that needs to be answered per language.
Perl has all four of {&& || and or} but they differ in their precedence. "and" and "or" have really low precedence so you can do things like "complex-function-call-here or die $!" and you won't accidentally have "or" slurp up something on its left side that you didn't want it to.
it depends on the language, but on PHP, I'd be careful about using && versus "and". The ones i often use are "&&" and "||"
http://us3.php.net/manual/en/language.operators.logical.php
$g = true && false; // $g will be assigned to (true && false) which is false
$h = true and false; // $h will be assigned to true
In some languages && will have a higher operator precedence than AND.
If both works fine, then I would say it's really personal preference, in most cases, they are compiled into same binary code like this : 11100010001000101001001010 [not real code, just an example].
&& = two keystrokes of the same key.
AND = three keystrokes of different keys.
I'm not sure what language you are using, but some languages differentiate between a normal boolean operator and a short-circuit operator. For example, the following are normal boolean operators in MATLAB:
C = or(A,B);
C = A | B; % Exactly the same as above
However, this is a short-circuit operator:
C = A || B;
The short-circuit syntax will evaluate the first argument and then, depending on the value, will potentially skip over evaluating the second argument. For example, if A is already true, B doesn't have to be evaluated for an OR operation, since the result is guaranteed to be true. This is helpful when B is replaced with a logical operation that involves some kind of expensive computation.
Here's a wikipedia link discussing short-circuit operators and their syntax for a few languages.
Unless there aren't any precedence issues, I'd say there are differences in readability. Consider the following:
if (&x == &y && &y == &z) {
// ..
}
#define AND &&
if (&x == &y AND &y == &z) {
// ..
}