Syntax Definition cab 1461

Description: Introduce the class builder or class abstraction notation ("the class of sets x such that φ is true"). Our class variables A, B, etc. range over class builders (implicitly in the case of defined class terms such as df-nul 2277). Note that a set variable can be expressed as a class builder per theorem cvjust 1469, justifying the assignment of set variables to class variables via the use of cv 953.

Hypotheses

Ref	Expression
wph	wff φ
vx	set x

Assertion

Ref	Expression
cab	class {x∣φ}

See definition df-clab 1462 for more information.

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