[Imprint][Data Privacy Statement][E-Mail]

View long theorem info. View the proof. Back to main index. View the specification. View theorem base summary, View theorem base listing, the used properties by spec, the dependency list, the symbol table,

Proof step 14 from proof postfix-split-stronger (previous step)

x.last = z.last, x.butlast ⊒ y + z.butlast, ∀ x0, y, z. # x0 < # x → x0 ⊒ y + z → x0 ⊒ z ∨ (∃ x1. x1 + z = x0 ∧ x1 ⊒ y) ⊦ y + z = [], x = [], z = [], x.butlast ⊒ z.butlast, ∃ x0. x0 + z = x ∧ x0 ⊒ y

User applied rule apply induction

And obtained the following new goals

Proof step 15:
x.last = z.last, x.butlast ⊒ y + z.butlast, ∀ x0, y, z. # x0 < # x → x0 ⊒ y + z → x0 ⊒ z ∨ (∃ x1. x1 + z = x0 ∧ x1 ⊒ y) ⊦ y + z = [], x = [], z = [], # x.butlast < # x, x.butlast ⊒ z.butlast, ∃ x0. x0 + z = x ∧ x0 ⊒ y

Rule argument

subst: [x0, y, z] → [x.butlast, y, z.butlast]

Additional information

Used simplifier rules: blapp: ⊦ x ≠ [] → (x.butlast = y ↔ x = y + x.last ');%butlast-last: x ≠ [] ⊦ x.butlast + x.last ' = x;%lapp: ⊦ y ≠ [] → (x + y).last = y.last;%lin-01: ⊦ x.last ∈ x ↔ x ≠ [];%bapp: ⊦ y ≠ [] → (x + y).butlast = x + y.butlast;%postfix-app-02: ⊦ y + x ⊒ z + x ↔ y ⊒ z;%in-15: ⊦ x + a ' = y → a ∈ y; (forward) from specification list%a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ a ∈ x + y ↔ a ∈ x ∨ a ∈ y; (s)% ⊦ x + y = z + y ↔ x = z; (s) Used terms: x.butlast, y, z.butlast