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Proof step 131 from proof bits2bits-sgn (previous step)

sgn(bytes2bits(bits2bytes(firstn(# bits - 8, bits)))) = sgn(firstn(# bits - 8, bits)), 8 < # bits, false ∈ bytes2bits(bits2bytes(firstn(# bits - 8, bits))), true ∈ bytes2bits(bits2bytes(firstn(# bits - 8, bits))), ∀ bits0. # bits0 < # bits → true → bits0 = [] ∨ sgn(bytes2bits(bits2bytes(bits0))) = sgn(bits0) ⊦ bits = [], sgn(firstn(# bits - 8, bits)) + byte2bits(i2b(bits2int(lastn(8, bits)))) = sgn(bits)

User applied rule insert rewrite lemma

And obtained the following new goals

Proof step 132:
⊦ # bits = 8 → byte2bits(i2b(bits2int(bits))) = bits
Proof step 133:
# lastn(8, bits) ≠ 8, sgn(bytes2bits(bits2bytes(firstn(# bits - 8, bits)))) = sgn(firstn(# bits - 8, bits)), 8 < # bits, false ∈ bytes2bits(bits2bytes(firstn(# bits - 8, bits))), true ∈ bytes2bits(bits2bytes(firstn(# bits - 8, bits))), ∀ bits0. # bits0 < # bits → true → bits0 = [] ∨ sgn(bytes2bits(bits2bytes(bits0))) = sgn(bits0) ⊦ bits = [], sgn(firstn(# bits - 8, bits)) + byte2bits(i2b(bits2int(lastn(8, bits)))) = sgn(bits)
Proof step 136:
# lastn(8, bits) = 8, sgn(bytes2bits(bits2bytes(firstn(# bits - 8, bits)))) = sgn(firstn(# bits - 8, bits)), 8 < # bits, false ∈ bytes2bits(bits2bytes(firstn(# bits - 8, bits))), true ∈ bytes2bits(bits2bytes(firstn(# bits - 8, bits))), ∀ bits0. # bits0 < # bits → true → bits0 = [] ∨ sgn(bytes2bits(bits2bytes(bits0))) = sgn(bits0) ⊦ bits = [], sgn(firstn(# bits - 8, bits)) + lastn(8, bits) = sgn(bits)

Rule argument

name: byte2bits8 rotate: F subst: [bits] → [lastn(8, bits)]

Additional information

Used terms: lastn(8, bits)