Definition df-base

Description: Define the base set (also called underlying set, ground set, carrier set, or carrier) extractor for extensible structures. (Contributed by NM, 4-Sep-2011) (Revised by Mario Carneiro, 14-Aug-2015) Use its index-independent form baseid instead. (New usage is discouraged.)

	Ref	Expression
Assertion	df-base	$$⊢\mathrm{Base}=\mathrm{Slot}1$$

Detailed syntax breakdown

Step	Hyp	Ref	Expression
0		cbs	$$class\mathrm{Base}$$
1		c1	$$class1$$
2	1	cslot	$$class\mathrm{Slot}1$$
3	0 2	wceq	$$wff\mathrm{Base}=\mathrm{Slot}1$$