definition preterm: Type[0] ≝ 𝒫❨path❩.
definition preterm_grafted: path → preterm → preterm ≝
- λp,t,q. p;;q ϵ t.
+ λp,t,q. p●q ϵ t.
interpretation
"grafted (preterm)"
'Pitchfork t p = (preterm_grafted p t).
definition preterm_root: preterm → preterm ≝
- λt,q. ∃r. q;;r ϵ t.
+ λt,q. ∃r. q●r ϵ t.
interpretation
"root (preterm)"