\Rightarrow (TLRef i) | false \Rightarrow (match (blt d i) with [true
\Rightarrow (TLRef (pred i)) | false \Rightarrow (lift d O v)])]) | (THead k
u t0) \Rightarrow (THead k (subst d v u) (subst (s k d) v t0))].
\Rightarrow (TLRef i) | false \Rightarrow (match (blt d i) with [true
\Rightarrow (TLRef (pred i)) | false \Rightarrow (lift d O v)])]) | (THead k
u t0) \Rightarrow (THead k (subst d v u) (subst (s k d) v t0))].