| # bits ≤ 1 + # bits1, ∀ bits1, bits0. # bits0 < # bits → # bits0 ≤ 1 + # bits1 → bits0 = [] ∨ bitsor(bits0, true ' + bits1) = bits0 ∨ false ∈ bits0 ⊦ bitsor(bits, true ' + bits1) = bits, bits = [], false ∈ bits |
⊦ 1 < # bits ∧ 1 < # bits0 → bitsor(bits, bits0) = bitsor(bits.butlast, bits0.butlast) + (bits.last ∨ bits0.last)
¬(1 < # bits ∧ 1 < #(true ' + bits1)), # bits ≤ 1 + # bits1, ∀ bits1, bits0. # bits0 < # bits → # bits0 ≤ 1 + # bits1 → bits0 = [] ∨ bitsor(bits0, true ' + bits1) = bits0 ∨ false ∈ bits0 ⊦ bitsor(bits, true ' + bits1) = bits, bits = [], false ∈ bits
1 < # bits ∧ 1 < #(true ' + bits1), # bits ≤ 1 + # bits1, ∀ bits1, bits0. # bits0 < # bits → # bits0 ≤ 1 + # bits1 → bits0 = [] ∨ bitsor(bits0, true ' + bits1) = bits0 ∨ false ∈ bits0 ⊦ bitsor(bits.butlast, (true ' + bits1).butlast) + (bits.last ∨ (true ' + bits1).last) = bits, bits = [], false ∈ bits
Used terms: true ' + bits1, bits