if every vector in a list has the same length, create a matrix

matrixIfAllSameLen <- function(a.list) {
if (length(unique(unlist(lapply(a.list, length)))) == 1) {
n <- length(a.list[[1]])
return(matrix(unlist(a.list), ncol=n, byrow=TRUE))
}
else {
return(a.list)
}
}