Definition df-base 17227

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 17229 instead. (New usage is discouraged.)

Assertion

Ref	Expression
df-base	⊢ Base = Slot 1

Detailed syntax breakdown of Definition df-base

Step	Hyp	Ref	Expression
1		cbs 17226	. 2 class Base
2		c1 11128	. . 3 class 1
3	2	cslot 17198	. 2 class Slot 1
4	1, 3	wceq 1540	1 wff Base = Slot 1

This definition is referenced by:  baseval  17228  baseid  17229  basendx  17235  sn-base0  42465