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Questions tagged [negation]

Negation is the logic operation that inverses a value, also seen as a NOT operation. Functions in specific languages may operate with negation to specific uses. For questions specific to the use of complement patterns in regular expressions, use [regex-negation] instead.

Negation is the logic operation that inverses a value, also seen as a NOT operation. Negation may be implemented by specific languages to provide functions capable of operating with values for specific uses.

Read also the wikipedia article on Negation.

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Prolog implying a negative predicate

How can I write the following rule in PROLOG: if P then not Q I understand that you can easily write if P then Q the predicates like q(X) :- p(X), but how can you negate the q/1 predicate? I don't want to define new predicates with other semantics…
Robert T.
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Logical Negation in Prolog

I've read quite a bit about Prolog's Negation by Failure where Prolog in order to prove that \+Goal holds tries to prove that Goal fails. This is highly connected with CWA (close world assumption) where for example if we query \+P(a) (where P is a…
coder
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Implementing logical negation with only bitwise operators (except !)

~ & ^ | + << >> are the only operations I can use Before I continue, this is a homework question, I've been stuck on this for a really long time. My original approach: I thought that !x could be done with two's complement and doing something with…
Jay
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How does the NEG instruction affect the flags on x86?

The Intel Software Development Manual says this about the neg instruction: The CF flag set to 0 if the source operand is 0; otherwise it is set to 1. The OF, SF, ZF, AF, and PF flags are set according to the result. I thought that AF and CF would…
tbodt
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Boolean "not equal to" in Lua (negation of a Boolean conditional)

How do I write an if statement in Lua that negates (inverts/flips) a Boolean variable used as the condition? For example, in Java, one can write: boolean a; a = false; if (!a) { //do something } I tried to replicate the above Java code in Lua…
Venkatesh
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Negating typescript types?

I wanted to create a simple NOT operator in typescript where you get all primitives combined into the union of some type A that are NOT primitive members of the union of a second type B. This can be done using conditional types. For example, if you…
Magnus
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Why double negation doesn't bind in Prolog

Say I have the following theory: a(X) :- \+ b(X). b(X) :- \+ c(X). c(a). It simply says true, which is of course correct, a(X) is true because there is no b(X) (with negation as finite failure). Since there is only a b(X) if there is no c(X) and…
Willem Van Onsem
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perl6 Negating multiple words and permutations of their chars inside a regex

What is the best way to perform, inside a regex, negation of multiple words and permutations of chars that make up those words? For instance: I do not want "zero dollar" "roze dollar" "eroz dollar" "one dollar" "noe dollar" "oen dollar" but I do…
lisprogtor
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Is there a way to negate @media min/max-width/height?

I use http://www.w3.org/TR/css3-mediaqueries/ to have different design depending on the available viewport. In order for my search-and-replace to work, for every time I decide to adjust the cut-off points, I'd like to clearly negate @media…
cnst
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swi-prolog negation

I've had a hard time searching for clear answers on negation in Prolog, so I apologize if this is an obvious question: I'm trying to write a simple code that will logically say that "X and Y love each other if X likes Y and only Y." My .pl code…
bjscollura
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jq: select when any value is in array

Given the input json [ {"title": "first line"}, {"title": "second line"}, {"title": "third line"} ] How can we extract only the titles that contain keywords that are listed in a second "filter" array. Using a shell variable here for…
Bernard
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Why the linux kernel uses double logical negations instead of casts to bools?

Given that x is a variable of type int with the number 5 as its value, consider the following statement: int y = !!x; This is what I think it happens: x is implicitly casted to a bool and the first negation is executed, after that the last negation…
Garmekain
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Repeated negation (!) operators in bash do not negate each other

So this is more an oddity I've come up against than something I really want to use. But I found something I didn't understand with the bash extended test syntax. Check this out (included my shell version in case it matters): 34>$SHELL --version GNU…
Swandog
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Negation of gsub | Replace everything except strings in a certain vector

I have a vector of strings: ve <- c("N","A","A","A","N","ANN","NA","NFNFNAA","23","N","A","NN", "parnot", "important", "notall") I want to keep only three possible values in this vector: N, A, and NA. Therefore, I want to replace any element that…
benett
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Idiomatically negate a filter

What's the most idiomatic way of writing a filter with a negation? Example: is_even= lambda x : x % 2 == 0 odd_numbers= filter( lambda x: not is_even(x), range(10) ) Of course, you can just use list comprehensions - but then you needn't use filter…
loopbackbee
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