to merge
add collision module. tested. very slow
add files
sid conllision
Merge branch 'master' of code.seas.harvard.edu:tianlan-cs207/tianlan-cs207
merge with collisioin with morton code
add new files
sid collision2
Merge branch 'master' of code.seas.harvard.edu:tianlan-cs207/tianlan-cs207
work collision
combine 2
sid collision
Merge branch 'master' of code.seas.harvard.edu:tianlan-cs207/tianlan-cs207
mypredicate
Merge with shallow water
disappear
merge succeed
code clean up
add commet
before specification