include "delayed_updating/substitution/fsubst.ma".
include "delayed_updating/syntax/prototerm_equivalence.ma".
include "delayed_updating/syntax/path_head.ma".
-include "delayed_updating/syntax/path_depth.ma".
include "delayed_updating/syntax/path_reverse.ma".
include "delayed_updating/notation/relations/black_rightarrow_f_4.ma".
λt1,t2. ∃n:pnat.
let r ≝ p●𝗔◗𝗟◗q in
∧∧ (𝗟◗q)ᴿ = ↳[n](rᴿ) & r◖𝗱n ϵ t1 &
- t1[⋔r←▼[𝐮❨♭(𝗟◗q)❩](t1⋔(p◖𝗦))] ⇔ t2
+ t1[⋔r←▼[𝐮❨n❩](t1⋔(p◖𝗦))] ⇔ t2
.
interpretation
- "focused balanced reduction with immediate updating (prototerm)"
+ "focused reduction with immediate updating (prototerm)"
'BlackRightArrowF t1 p q t2 = (ifr p q t1 t2).