Syntax Definition cab 2026

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 (sometimes implicitly). Note that a setvar variable can be expressed as a class builder per theorem cvjust 2035, justifying the assignment of setvar variables to class variables via the use of cv 1242.

Hypotheses

Ref	Expression
wph	wff 𝜑
vx	setvar 𝑥

Assertion

Ref	Expression
cab	class {𝑥 ∣ 𝜑}

See definition df-clab 2027 for more information.