flip certain bits in vector

try this:

b <- c(1, 0, 1, 0, 1, 0, 1, 0, 1, 0)
p <- c(1, 3, 5, 7)
b[p] <- ifelse(b[p] == 0, 1, 0)

I'll have to look up the ifelse operator, looks like
the ternary operator used in C

b[p] = b[p]==0?1:0

Cool - thanks!

Esmail