| ⊦ char ' + str0 = "", substring(char ' + str0, m0 + 1, n) = substring(str0, m0, n) |
⊦ substring(str, m, n) = l→s(sublist(m, n, s→l(str)))
⊦ char ' + str0 = "", l→s(sublist(m0 + 1, n, s→l(char ' + str0))) = substring(str0, m0, n)
Used terms: n, m0 + 1, char ' + str0