# Questions tagged [notation]

Use this tag whenever you have a question about what some particular symbol/notation means.

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### What does an = sign with an x beneath it mean?

I am studying for a test in Logic right now, and saw the symbol $\underset{x}{=}$, which is used like this: $I \underset{x}{=} I'$. I've seen it in the solutions of questions like this one: Prove ...
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### Clarification notation in CLRS runtime analysis

I am learning algorithms from the clrs book. I am having trouble understanding the notation the book has placed. The book wrote the following: $t_j$ denote the number of times the ...
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### What does $CS - CF$ means?

What does $L_1 \in CS - CF$ means? I think the meaning is $L_1$ can be generated by context-sensitive grammars, but cannot be generated by context-free grammars. Am I understanding this correctly? ...
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### Notation: $L_R = \{w\#y\space|\space R(w,y)\}$?

What is the set $$L_R = \{w\#y\space|\space R(w,y)\}$$ Specifically what kind of conditional is $R(w,y)$? Also what's the purpose of $\#$? This comes from page 2 of the Clay paper on P vs NP: http://...
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### What does this mean $[X]_1^T$?

I found this in information theory paper, P.3883* the authors states the following Most existing theoretic studies of network coding focus on DAGs due to its simpler structure and dure to the ...
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### What is a conventional format for presenting algorithms?

I'm writing a technical paper and the review committee wants my methodology to be represented in a conventional algorithm format. I've been searching all over the web for the conventional structure ...
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### Selection type generated by nested loops where initial value is current value of parent loop

Consider the generator of the selections: ...
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### Principles of Programming Languages: Understanding Judgements

I am taking a principles of programming languages class right now and am trying to understand the following judgement form. ...
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### Use of Big O Notation in a recent paper by Khot et al

I'm reading a paper about Constraint Satisfaction Problems, specifically "A Characterization of Strong Approximation Resistance", Subhash Khot, Madhur Tulsiani, Pratik Worah (ECCC TR13-075). The ...
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### Origins of misconception about using equality signs with Landau notation

From "Misconception 1" from Søren S. Pedersen's blog, and as many have seen before, a major misconception in Big-O (and others) notation is to say a function is "equal" to Big-O of some other function:...
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### What does superscript + mean in relational algebra?

What does superscript + mean in relational algebra? Suppose $A$ is a subset of attributes of all attributes in a relation $R$. What does $A^+$ mean?
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### In type systems, is there a name for SQL's way of cutting and combining record types into new types?

I'd like to have this feature in my application programming language (which these days, is Scala), but when I went to learn more about it on the internets, I realized I don't know the name of it. I'm ...
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### Numeral systems other than unary used in nature or in animal and human behaviours

Representing numeric values using positional notation is one of the milestones in the history of arithmetic. Babylons used a base 60 system, Maya a base 20 system; base 10 system became "the standard" ...
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### Notation for average case complexity of an algorithm

I'm just wondering what the correct notation is when referring to an average case complexity of an algorithm that was calculated by doing empirical analysis. For example, I have tested my algorithm ...
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### What are these notations O(1)/O(n)/O(log n)? [duplicate]

I am a newbie here I recently read tutorials on java about collection framework. The time complexity of various objects in reading/writing data What does it mean? ...
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### Correct mapping “update” notation for computer science papers

A nice easy one. I'm interested to know the most standard and accepted way to denote the update of a mapping in the context of a theoretical computer science paper. By example, suppose we have a ...