BEGIN {
a[i] = "null" # i is initially undefined
for (i in a) { # i is null string
print length(i), a[i] # , typeof(i) # 0 null
print (i==0), (i=="") # 1 1 should be 0 1
}
print a[""] # null
print a[0] #
b[$2] = "null also" # $2 is also undefined
for (j in b) {
print length(j), a[j] # , typeof(i) # 0 null
print (j==0), (j=="") # 1 1 should be 0 1
}
print b[""] # null
print b[0] #
}