Computational Example 3.5
rsite <- function(inseq, seq){
  # inseq: vector containing input DNA sequence,
  # A=1, C=2, G=3, and T =4
  # seq: vector for restriction site, length m, coded as above.
  # Make/initialize vector to hold site
  # positions found in inseq
  xxx <- rep(0, length(inseq))
  m <- length(seq) # Length of restriction recognition sequence
  truth <- rep(0, m) # To record whether pos. of inseq match seq
 	 # Check each position to see if a site starts there.
	 for(i in 1:(length(inseq) - (length(seq) - 1))) {
	for(j in 1:m) {
		 if(inseq[i + j - 1] == seq[j]) {
		 truth[j] <- 1 # Record match to jth pos.
  		}
	}
if(sum(truth[]) == m){ # Check whether all positions match
	xxx[i] <- i # Record site if all positions match
	}
 truth <- rep(0, m) # Reinitialize for next loop cycle
 # Write vector of restriction site positions stored in xxx.
 L <- xxx[xxx > 0]
 return(L)
}