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Proof step 2 from proof len-str (previous step)

⊦ str ≠ "" → # str = # str.rstring + 1

Heuristic simplifier applied rule simplifier

And closed the goal!

Rule argument

Additional information

Used simplifier rules: a: ⊦ (m + n0) + n1 = m + n0 + n1; from specification nat-basic2%c: ⊦ m + n = n + m; from specification nat-basic2%eq-02: n ≤ m ⊦ (m - n) + n0 = n1 ↔ m + n0 = n + n1; from specification nat%l: ⊦ # str = 0 ↔ str = ""; from specification list-data[string-new]%one-01: ⊦ m < 1 ↔ m = 0; from specification nat-basic1%lels-01: ⊦ ¬ m ≤ n ↔ n < m; from specification nat%pred-03: ⊦ n -1 = n - 1; from specification nat%length-rest: ⊦ str ≠ "" → # str.rstring = (# str)-1; from specification list-data[string-new]