Allow less thans in a chain

less_chain

less_chain <- function(.a,a,b,equal=FALSE){
  if(length(a) != length(b) && (length(a) != 1 && length(b) != 1))
    stop("Incompatible lengths",call.=FALSE)
  if(is.call(.a) &&
     (identical(.a[[1]],quote(`%<%`)) || identical(.a[[1]],quote(`%<=%`)))){
    mid <- eval(.a[[3]])
    rhs <- if(equal) mid <= b else mid < b
    a & rhs
  } else if(is.numeric(a) && is.numeric(b)){
    if(equal) a <= b else a < b
  } 
}

`%<%` <- function(a,b){
  less_chain(substitute(a),eval(a),b,FALSE)
}

`%<=%` <- function(a,b){
  less_chain(substitute(a),eval(a),b,TRUE)
}


x <- 1:10

3 %<% x %<% 6

6 %<=% x %<% 10

1:2 %<% 2:4