[check 'abcdefghi'] len = 9
sub(0, 9) == 'abcdefghi'
sub(0, 0) == ''
sub(1, 9) == 'bcdefghi'
sub(0, 1) == 'a'
sub(2, 9) == 'cdefghi'
sub(0, 2) == 'ab'
sub(3, 9) == 'defghi'
sub(0, 3) == 'abc'
sub(4, 9) == 'efghi'
sub(0, 4) == 'abcd'
sub(5, 9) == 'fghi'
sub(0, 5) == 'abcde'
sub(6, 9) == 'ghi'
sub(0, 6) == 'abcdef'
sub(7, 9) == 'hi'
sub(0, 7) == 'abcdefg'
sub(8, 9) == 'i'
sub(0, 8) == 'abcdefgh'

[check 'bcdefgh'] len = 7
sub(0, 7) == 'bcdefgh'
sub(0, 0) == ''
sub(1, 7) == 'cdefgh'
sub(0, 1) == 'b'
sub(2, 7) == 'defgh'
sub(0, 2) == 'bc'
sub(3, 7) == 'efgh'
sub(0, 3) == 'bcd'
sub(4, 7) == 'fgh'
sub(0, 4) == 'bcde'
sub(5, 7) == 'gh'
sub(0, 5) == 'bcdef'
sub(6, 7) == 'h'
sub(0, 6) == 'bcdefg'

[check 'cdefg'] len = 5
sub(0, 5) == 'cdefg'
sub(0, 0) == ''
sub(1, 5) == 'defg'
sub(0, 1) == 'c'
sub(2, 5) == 'efg'
sub(0, 2) == 'cd'
sub(3, 5) == 'fg'
sub(0, 3) == 'cde'
sub(4, 5) == 'g'
sub(0, 4) == 'cdef'

[check 'def'] len = 3
sub(0, 3) == 'def'
sub(0, 0) == ''
sub(1, 3) == 'ef'
sub(0, 1) == 'd'
sub(2, 3) == 'f'
sub(0, 2) == 'de'

[check 'e'] len = 1
sub(0, 1) == 'e'
sub(0, 0) == ''

[check 'abcdefgh'] len = 8
sub(0, 8) == 'abcdefgh'
sub(0, 0) == ''
sub(1, 8) == 'bcdefgh'
sub(0, 1) == 'a'
sub(2, 8) == 'cdefgh'
sub(0, 2) == 'ab'
sub(3, 8) == 'defgh'
sub(0, 3) == 'abc'
sub(4, 8) == 'efgh'
sub(0, 4) == 'abcd'
sub(5, 8) == 'fgh'
sub(0, 5) == 'abcde'
sub(6, 8) == 'gh'
sub(0, 6) == 'abcdef'
sub(7, 8) == 'h'
sub(0, 7) == 'abcdefg'

[check 'bcdefg'] len = 6
sub(0, 6) == 'bcdefg'
sub(0, 0) == ''
sub(1, 6) == 'cdefg'
sub(0, 1) == 'b'
sub(2, 6) == 'defg'
sub(0, 2) == 'bc'
sub(3, 6) == 'efg'
sub(0, 3) == 'bcd'
sub(4, 6) == 'fg'
sub(0, 4) == 'bcde'
sub(5, 6) == 'g'
sub(0, 5) == 'bcdef'

[check 'cdef'] len = 4
sub(0, 4) == 'cdef'
sub(0, 0) == ''
sub(1, 4) == 'def'
sub(0, 1) == 'c'
sub(2, 4) == 'ef'
sub(0, 2) == 'cd'
sub(3, 4) == 'f'
sub(0, 3) == 'cde'

[check 'de'] len = 2
sub(0, 2) == 'de'
sub(0, 0) == ''
sub(1, 2) == 'e'
sub(0, 1) == 'd'

[check ''] len = 0

[check 'abcdefg'] len = 7
sub(0, 7) == 'abcdefg'
sub(0, 0) == ''
sub(1, 7) == 'bcdefg'
sub(0, 1) == 'a'
sub(2, 7) == 'cdefg'
sub(0, 2) == 'ab'
sub(3, 7) == 'defg'
sub(0, 3) == 'abc'
sub(4, 7) == 'efg'
sub(0, 4) == 'abcd'
sub(5, 7) == 'fg'
sub(0, 5) == 'abcde'
sub(6, 7) == 'g'
sub(0, 6) == 'abcdef'

[check 'bcdef'] len = 5
sub(0, 5) == 'bcdef'
sub(0, 0) == ''
sub(1, 5) == 'cdef'
sub(0, 1) == 'b'
sub(2, 5) == 'def'
sub(0, 2) == 'bc'
sub(3, 5) == 'ef'
sub(0, 3) == 'bcd'
sub(4, 5) == 'f'
sub(0, 4) == 'bcde'

[check 'cde'] len = 3
sub(0, 3) == 'cde'
sub(0, 0) == ''
sub(1, 3) == 'de'
sub(0, 1) == 'c'
sub(2, 3) == 'e'
sub(0, 2) == 'cd'

[check 'd'] len = 1
sub(0, 1) == 'd'
sub(0, 0) == ''

[check 'abcdef'] len = 6
sub(0, 6) == 'abcdef'
sub(0, 0) == ''
sub(1, 6) == 'bcdef'
sub(0, 1) == 'a'
sub(2, 6) == 'cdef'
sub(0, 2) == 'ab'
sub(3, 6) == 'def'
sub(0, 3) == 'abc'
sub(4, 6) == 'ef'
sub(0, 4) == 'abcd'
sub(5, 6) == 'f'
sub(0, 5) == 'abcde'

[check 'bcde'] len = 4
sub(0, 4) == 'bcde'
sub(0, 0) == ''
sub(1, 4) == 'cde'
sub(0, 1) == 'b'
sub(2, 4) == 'de'
sub(0, 2) == 'bc'
sub(3, 4) == 'e'
sub(0, 3) == 'bcd'

[check 'cd'] len = 2
sub(0, 2) == 'cd'
sub(0, 0) == ''
sub(1, 2) == 'd'
sub(0, 1) == 'c'

[check ''] len = 0

[check 'abcde'] len = 5
sub(0, 5) == 'abcde'
sub(0, 0) == ''
sub(1, 5) == 'bcde'
sub(0, 1) == 'a'
sub(2, 5) == 'cde'
sub(0, 2) == 'ab'
sub(3, 5) == 'de'
sub(0, 3) == 'abc'
sub(4, 5) == 'e'
sub(0, 4) == 'abcd'

[check 'bcd'] len = 3
sub(0, 3) == 'bcd'
sub(0, 0) == ''
sub(1, 3) == 'cd'
sub(0, 1) == 'b'
sub(2, 3) == 'd'
sub(0, 2) == 'bc'

[check 'c'] len = 1
sub(0, 1) == 'c'
sub(0, 0) == ''

[check 'abcd'] len = 4
sub(0, 4) == 'abcd'
sub(0, 0) == ''
sub(1, 4) == 'bcd'
sub(0, 1) == 'a'
sub(2, 4) == 'cd'
sub(0, 2) == 'ab'
sub(3, 4) == 'd'
sub(0, 3) == 'abc'

[check 'bc'] len = 2
sub(0, 2) == 'bc'
sub(0, 0) == ''
sub(1, 2) == 'c'
sub(0, 1) == 'b'

[check ''] len = 0

[check 'abc'] len = 3
sub(0, 3) == 'abc'
sub(0, 0) == ''
sub(1, 3) == 'bc'
sub(0, 1) == 'a'
sub(2, 3) == 'c'
sub(0, 2) == 'ab'

[check 'b'] len = 1
sub(0, 1) == 'b'
sub(0, 0) == ''

[check 'ab'] len = 2
sub(0, 2) == 'ab'
sub(0, 0) == ''
sub(1, 2) == 'b'
sub(0, 1) == 'a'

[check ''] len = 0

[check 'a'] len = 1
sub(0, 1) == 'a'
sub(0, 0) == ''