Assigning to multiple variables on same line

[Yang Zhang]

Why does assigning to multiple variables on the same line exhibit 
sequential consistency normally but not for local variables?

#!/usr/bin/env bash
f() {
  local a=$1 b=$a
  c=0 d=$c
  echo $b
  echo $d
}
f x
# Output:
# b=
# d=0
--
Yang Zhang
http://www.mit.edu/~y_z/