outline.R

# outline <- c("a", "b")
# print_outline(outline):
# - a
# - b
# print_outline(outline, 1):
# - **a**
# - b
# ---
# outline <- list("a" = c("b", "c", "d"), "e" = NULL, "f" = NULL)
# print_outline(outline):
# - a
#     - b
#     - c
#     - d
# - e
# - f
# print_outline(outline, 1)
# print_outline(outline, 2)

get_prefix <- function(level, incremental) {
	sprintf("%s%s- ", ifelse(incremental, "", "> "), ifelse(level == 0, "", rep("    ", level)))
}

get_current <- function(current, retval) {
	if (current == 0) return(retval)
	retval[current] <- sprintf("**%s**", retval[current])
	return(retval)	
}

print_outline <- function(outline, current = 0, level = 0, incremental = TRUE) {
	if(is.null(outline)) {
		return(NULL)
	}
	if(class(outline) == "character") {
		prefix <- get_prefix(level, incremental)
		outline <- get_current(current, outline)
		retval <- paste(prefix, outline, sep="")
		return(retval)
	}
	stopifnot(class(outline) == "list")
	prefix <- get_prefix(level, incremental)
	retval <- c()
	for(i in 1:length(outline)) {
		if (i == current) {
			add_line <- paste(prefix, "**", names(outline)[i], "**", sep="")
		} else {
			add_line <- paste(prefix, names(outline)[i], sep="")
		}
		retval <- c(retval, add_line)
		force(level)
		if (i == current) {
			add_line <- print_outline(outline[[i]], level=level+1, incremental=incremental, current=0)
			retval <- c(retval, add_line)
		}
	}
	return(retval)
}