| m < 10, ∀ m1. m1 < m → true → s→n(n→s(m1)) = m1 ⊦ s→n(('0' ' + '1' ' + '2' ' + '3' ' + '4' ' + '5' ' + '6' ' + '7' ' + '8' ' + '9' ')[m] ') = m |
⊦ s→n(char ') = pos(char, '0' + '1' + '2' + '3' + '4' + '5' + '6' + '7' + ('8' + '9'))
m < 10, ∀ m1. m1 < m → true → s→n(n→s(m1)) = m1 ⊦ pos (('0' ' + '1' ' + '2' ' + '3' ' + '4' ' + '5' ' + '6' ' + '7' ' + '8' ' + '9' ')[m], '0' + '1' + '2' + '3' + '4' + '5' + '6' + '7' + ('8' + '9')) = m
Used terms: ( '0' ' + '1' ' + '2' ' + '3' ' + '4' ' + '5' ' + '6' ' + '7' ' + '8' ' + '9' ' )[m ]