- | #a; #a'; #Ha; nwhd in ⊢ (? ? ? % %); napply mk_iff; *; #H1; #H2; napply conj
- [##1,2: napply (. (mem_ok' …)^-1) [##3,6: nassumption |##2,5: nassumption |##*: ##skip]
- ##|##3,4: napply (. (mem_ok' …)) [##1,3,4,6: nassumption |##*: ##skip]##]##]
- ##| #a; #a'; #b; #b'; #Ha; #Hb; nwhd; napply conj; #x; nwhd in ⊢ (% → %); #H
- [ napply (. ((#‡Ha^-1)‡(#‡Hb^-1))); nassumption
+ | #a; #a'; #Ha;
+ nwhd in ⊢ (? ? ? % %); @; *; #H1; #H2; @
+ [##1,2: napply (. Ha^-1‡#); nassumption;
+ ##|##3,4: napply (. Ha‡#); nassumption]##]
+ ##| #a; #a'; #b; #b'; #Ha; #Hb; nwhd; @; #x; nwhd in ⊢ (% → %); #H
+ [ alias symbol "invert" = "setoid1 symmetry".
+ napply (. ((#‡Ha^-1)‡(#‡Hb^-1))); nassumption