change type of length to integer
continue working on ReadThenWrite
add post condition on bitpos
save current state
save proof attempt
fix wrong post condition
minor
rewrite default post condition (increment)
try to concentrate on most important post condition
remove statement contracts
simplify signature of ReadThenWrite
start rewriting
add statement contracts
save proof state
Merge branch 'master' into refactor
add shift_different lemma
minor
save proof state
add Old label (still unclear)
add example for potential bug report