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Proof step 2 from proof append-eqlen (previous step)

# str = # str1, str + str0 = str1 + str2 ⊦ str = str1 ∧ str0 = str2

User applied rule structural induction

And obtained the following new goals

Proof step 3:
∀ str1, str0, str2. # str3 = # str1 ∧ str3 + str0 = str1 + str2 → str3 = str1 ∧ str0 = str2, #(char + str3) = # str1, (char + str3) + str0 = str1 + str2 ⊦ char + str3 = str1 ∧ str0 = str2

Rule argument

indvar: str

Additional information

Used simplifier rules: Length-empty: ⊦ # "" = 0;%len-zero: ⊦ # str = 0 ↔ str = "";%string freely generated by "", +;;%append-base: ⊦ "" + str = str; from specification string-append%assoc: ⊦ (str1 + str2) + str3 = str1 + str2 + str3; from specification string-append