| ⊦ str0 = "", str < str + str0 |
∀ str0. str0 = "" ∨ str1 < str1 + str0 ⊦ str0 = "", char + str1 < (char + str1) + str0
Used simplifier rules: less-empty: ⊦ "" < str ↔ str ≠ "";%string freely generated by "", +;;%append-base: ⊦ "" + str = str; from specification string-append%assoc: ⊦ (str1 + str2) + str3 = str1 + str2 + str3; from specification string-append