| '6' ' + '7' ' + '8' ' + '9' ' ≠ [] ∧ m ≠ 0, m < 4, ∀ m1, char. m1 < (((((m + 1) + 1) + 1) + 1) + 1) + 1 → true → ¬ char ∈ '0' + '1' + '2' + '3' + '4' + '5' + '6' + '7' + ('8' + '9') → ¬ char ∈ s→l(n→s(m1)) ⊦ ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '1', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '2', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '3', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '4', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '5', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '6', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '7', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '8', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '9', ('6' ' + '7' ' + '8' ' + '9' ').rest[m - 1] = '0' |
m < 4, ∀ m1, char. m1 < (((((m + 1) + 1) + 1) + 1) + 1) + 1 → true → ¬ char ∈ '0' + '1' + '2' + '3' + '4' + '5' + '6' + '7' + ('8' + '9') → ¬ char ∈ s→l(n→s(m1)) ⊦ m = 0, ('7' ' + '8' ' + '9' ')[m - 1] = '1', ('7' ' + '8' ' + '9' ')[m - 1] = '2', ('7' ' + '8' ' + '9' ')[m - 1] = '3', ('7' ' + '8' ' + '9' ')[m - 1] = '4', ('7' ' + '8' ' + '9' ')[m - 1] = '5', ('7' ' + '8' ' + '9' ')[m - 1] = '6', ('7' ' + '8' ' + '9' ')[m - 1] = '7', ('7' ' + '8' ' + '9' ')[m - 1] = '8', ('7' ' + '8' ' + '9' ')[m - 1] = '9', ('7' ' + '8' ' + '9' ')[m - 1] = '0'
Used simplifier rules: ⊦ char ' + chars ≠ [];% ⊦ (chars + chars0) + chars1 = chars + chars0 + chars1;% ⊦ (char ' + chars).rest = chars;