Content deleted Content added
Tag: Reverted |
Tag: Reverted |
||
Line 26:
</math>
The [[Iverson bracket]] provides the equivalent notation, <math>[x\in A]</math> or {{nowrap|{{math|⧙ ''x'' ϵ ''A'' ⧘}},}} to be used instead of <math>\mathbf{
The function <math>\mathbf{1}_A</math> is sometimes denoted {{mvar|I<sub>A</sub>}}, {{mvar|χ<sub>A</sub>}}, {{mvar|K<sub>A</sub>}}, or even just {{mvar|A}}.{{efn|name=χαρακτήρ|The [[Greek alphabet|Greek letter]] {{mvar|χ}} appears because it is the initial letter of the Greek word {{lang|grc|χαρακτήρ}}, which is the ultimate origin of the word ''characteristic''.}}{{efn|The set of all indicator functions on {{mvar|X}} can be identified with <math>\mathcal{P}(X),</math> the [[power set]] of {{mvar|X}}. Consequently, both sets are sometimes denoted by <math>2^X.</math> This is a special case (<math>Y = \{0,1\} = 2</math>) of the notation <math>Y^X</math> for the set of all functions <math>f:X \to Y.</math>}}
| |||