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Theorem bj-charfunr 15945

Description: If a class

has a "weak" characteristic function on a class

, then negated membership in

is decidable (in other words, membership in

is testable) in

The hypothesis imposes that be a set. As usual, it could be formulated as $/\$ to deal with general classes, but that extra generality would not make the theorem much more useful.

The theorem would still hold if the codomain of were any class with testable equality to the point where $\$ is sent. (Contributed by BJ, 6-Aug-2024.)

**Hypothesis**
Ref	Expression
bj-charfunr.1	$/\$ $\$

**Assertion**
Ref	Expression
bj-charfunr	DECID

Distinct variable groups:

Allowed substitution hints:

(

)

(

)

**Proof of Theorem bj-charfunr**
Step	Hyp	Ref	Expression
1		bj-charfunr.1	. . . . 5 $/\$ $\$
2		elmapi 6780	. . . . . . . . . 10
3		ffvelcdm 5736	. . . . . . . . . . 11 $/\$
4	3	ex 115	. . . . . . . . . 10
5	2, 4	syl 14	. . . . . . . . 9
6		0elnn 4685	. . . . . . . . . 10 $\/$
7		nn0eln0 4686	. . . . . . . . . . 11
8	7	orbi2d 792	. . . . . . . . . 10 $\/$ $\/$
9	6, 8	mpbid 147	. . . . . . . . 9 $\/$
10	5, 9	syl6 33	. . . . . . . 8 $\/$
11	10	adantr 276	. . . . . . 7 $/\$ $/\$ $\$ $\/$
12		elin 3364	. . . . . . . . . . . . . . 15 $/\$
13		rsp 2555	. . . . . . . . . . . . . . 15
14	12, 13	biimtrrid 153	. . . . . . . . . . . . . 14 $/\$
15	14	expd 258	. . . . . . . . . . . . 13
16	15	adantr 276	. . . . . . . . . . . 12 $/\$ $\$
17	16	imp 124	. . . . . . . . . . 11 $/\$ $\$ $/\$
18	17	necon2bd 2436	. . . . . . . . . 10 $/\$ $\$ $/\$
19		eldif 3183	. . . . . . . . . . . . . . 15 $\$ $/\$
20		rsp 2555	. . . . . . . . . . . . . . 15 $\$ $\$
21	19, 20	biimtrrid 153	. . . . . . . . . . . . . 14 $\$ $/\$
22	21	expd 258	. . . . . . . . . . . . 13 $\$
23	22	adantl 277	. . . . . . . . . . . 12 $/\$ $\$
24	23	imp 124	. . . . . . . . . . 11 $/\$ $\$ $/\$
25	24	necon3ad 2420	. . . . . . . . . 10 $/\$ $\$ $/\$
26	18, 25	orim12d 788	. . . . . . . . 9 $/\$ $\$ $/\$ $\/$ $\/$
27	26	ex 115	. . . . . . . 8 $/\$ $\$ $\/$ $\/$
28	27	adantl 277	. . . . . . 7 $/\$ $/\$ $\$ $\/$ $\/$
29	11, 28	mpdd 41	. . . . . 6 $/\$ $/\$ $\$ $\/$
30	29	adantl 277	. . . . 5 $/\$ $/\$ $/\$ $\$ $\/$
31	1, 30	rexlimddv 2630	. . . 4 $\/$
32	31	imp 124	. . 3 $/\$ $\/$
33		df-dc 837	. . 3 DECID $\/$
34	32, 33	sylibr 134	. 2 $/\$ DECID
35	34	ralrimiva 2581	1 DECID

Colors of variables: wff set class

Syntax hints:

wn 3

wi 4 $/\$ wa 104 $\/$ wo 710 DECID wdc 836

wceq 1373

wcel 2178

wne 2378

wral 2486

wrex 2487 $\$ cdif 3171

cin 3173

c0 3468

com 4656

wf 5286

cfv 5290 (class class class)co 5967

cmap 6758

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 106 ax-ia2 107 ax-ia3 108 ax-in1 615 ax-in2 616 ax-io 711 ax-5 1471 ax-7 1472 ax-gen 1473 ax-ie1 1517 ax-ie2 1518 ax-8 1528 ax-10 1529 ax-11 1530 ax-i12 1531 ax-bndl 1533 ax-4 1534 ax-17 1550 ax-i9 1554 ax-ial 1558 ax-i5r 1559 ax-13 2180 ax-14 2181 ax-ext 2189 ax-sep 4178 ax-nul 4186 ax-pow 4234 ax-pr 4269 ax-un 4498 ax-setind 4603 ax-iinf 4654

This theorem depends on definitions: df-bi 117 df-dc 837 df-3an 983 df-tru 1376 df-fal 1379 df-nf 1485 df-sb 1787 df-eu 2058 df-mo 2059 df-clab 2194 df-cleq 2200 df-clel 2203 df-nfc 2339 df-ne 2379 df-ral 2491 df-rex 2492 df-v 2778 df-sbc 3006 df-dif 3176 df-un 3178 df-in 3180 df-ss 3187 df-nul 3469 df-pw 3628 df-sn 3649 df-pr 3650 df-op 3652 df-uni 3865 df-int 3900 df-br 4060 df-opab 4122 df-id 4358 df-suc 4436 df-iom 4657 df-xp 4699 df-rel 4700 df-cnv 4701 df-co 4702 df-dm 4703 df-rn 4704 df-iota 5251 df-fun 5292 df-fn 5293 df-f 5294 df-fv 5298 df-ov 5970 df-oprab 5971 df-mpo 5972 df-map 6760

This theorem is referenced by: bj-charfunbi 15946

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