#
# Helper functions
#

# Create a column vector (matrix with a single column in R) for the given list l.
# Ex. x = vec(c(1.2, 2.4))
vec <- function(l) {
  len = length(l);
  v <- matrix(l, nrow=len, ncol=1);
  return(v)
}
# Create a matrix for the given list l with the given number of rows(r) and column(r)
# Ex. x = mat(c(1,2,3,4), 2, 2)
mat <- function(l, r, c, byrow=TRUE) {
  len = length(l);
  if(!(len = r*c)) {
    print("Error in mat(): length of l must be r x c")
    return (NULL);
  }
  m <- matrix(l, nrow=r, ncol=c, byrow=byrow);
  return(m)
}

#
# Compute the inverse of a square matrix A
#
inv <- function(A) {
  return(solve(A))
}

#
# Compute the 2-norm of a vector or a matrix
#
#norm2 <- function(A) {
#  return(norm(A, type="2"))
#}

norminf <- function(A) {
  return(norm(A, type="i"))
}