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Proof step 1 from proof s2l-length (conclusion)

⊦ # s→l(str) = # str

User applied rule structural induction

And closed the goal!

Rule argument

indvar: str

Additional information

Used simplifier rules: s2l-empty: ⊦ s→l("") = [];%s2l-app: ⊦ s→l(str + str0) = s→l(str) + s→l(str0);%s2l-one: ⊦ s→l(char ') = char ';%string freely generated by "", +;;% ⊦ # "" = 0;% ⊦ # [] = 0;% ⊦ char + str = char ' + str;% ⊦ (str1 + str2) + str3 = str1 + str2 + str3;% ⊦ #(chars + chars0) = # chars + # chars0;% ⊦ # char ' = 0 +1;% ⊦ (chars + chars0) + chars1 = chars + chars0 + chars1;% ⊦ #(char ' + str) = # str + 1;% ⊦ m + n = m + n0 ↔ n = n0;% ⊦ (m + n0) + n1 = m + n0 + n1;% ⊦ m + n = n + m;