Syntax Definition cab 2339

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 3552). Note that a setvar variable can be expressed as a class builder per Theorem cvjust 2348, justifying the assignment of setvar variables to class variables via the use of cv 1641.

Hypotheses

Ref	Expression
wph	wff φ
vx	setvar x

Assertion

Ref	Expression
cab	class {x ∣ φ}

See definition df-clab 2340 for more information.