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dummy edit to complete interrupted edit summary: I do not think "there should be some evidence of use before adding a new bolded word to the first paragraph of an article" is an unreasonable standard to apply Tag: Reverted |
Undid dummy edit 1251539483: I agree that without the redirect, there is no need for mentioning (let alone bolding) the notion here |
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When [[Function (mathematics)#Arrow notation|arrow notation]] is used for functions, a partial function <math>f</math> from <math>X</math> to <math>Y</math> is sometimes written as <math>f : X \rightharpoonup Y,</math> <math>f : X \nrightarrow Y,</math> or <math>f : X \hookrightarrow Y.</math> However, there is no general convention, and the latter notation is more commonly used for [[inclusion map]]s or [[embedding]]s.{{citation needed|reason=Provide a few example citations for each notation.|date=July 2019}}
Specifically, for a partial function <math>f : X \rightharpoonup Y,</math> and any <math>x \in X,</math> one has either:
* <math>f(x) = y \in Y</math> (it is a single element in {{mvar|Y}}), or
* <math>f(x)</math> is undefined.
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