Definition df-s2 11549

Description: Define the length 2 word constructor. (Contributed by Mario Carneiro, 26-Feb-2016.)

Assertion

Ref	Expression
df-s2	|- <" A B "> = ( <" A "> ++ <" B "> )

Detailed syntax breakdown of Definition df-s2

Step	Hyp	Ref	Expression
1		cA	. . 3 class A
2		cB	. . 3 class B
3	1, 2	cs2 11542	. 2 class <" A B ">
4	1	cs1 11404	. . 3 class <" A ">
5	2	cs1 11404	. . 3 class <" B ">
6		cconcat 11379	. . 3 class ++
7	4, 5, 6	co 6088	. 2 class ( <" A "> ++ <" B "> )
8	3, 7	wceq 1402	1 wff <" A B "> = ( <" A "> ++ <" B "> )

This definition is used by:  cats2catd  11562  s2eqd  11563  s2cld  11571  s2fv0g  11580  s2fv1g  11581  s2leng  11582  s1s2d  11587  s2s2d  11593  s4s2d  11594  s2s5d  11597  s5s2d  11598  konigsberglem1  16951  konigsberglem2  16952  konigsberglem3  16953