对于与字符串相关的所有内容，尤其是关于定制消息（警告、错误等），我尽量坚持 80 个字符的打印边距。
现在，我一直想知道是否有一种简单的方法可以确保自动确保/强制执行某些打印边距限制，例如，如果给定的原子字符串超过了所选的打印边距，则会自动将其分解为字符串向量。我用谷歌搜索了一下，但并没有真正找到适合我需要的东西。
问题
有人想出了一个不错的“漂亮打印”功能，但我可以进一步构建吗？
到目前为止，这是我自己想出的：
函数定义
makePretty <- function(
string,
print.margin=80,
...
){
out <- string
if (nchar(string) > print.margin) {
times <- ceiling(nchar(string)/print.margin)
breaks <- rep(print.margin+1, times)
breaks <- cumsum(breaks)
string.spl <- unlist(strsplit(string, split=" "))
seps <- str_locate_all(string, " ")[[1]][,"start"]
queue <- NA
envir <- environment()
out <- unlist(sapply(1:length(breaks), function(ii) {
idx.next <- breaks[ii]
if (ii < length(breaks)) {
idx <- which(seps <= idx.next)
chunk <- string.spl[idx]
envir$string.spl <- envir$string.spl[-idx]
envir$seps <- envir$seps[-idx]
} else {
chunk <- string.spl
}
chunk <- paste(chunk, collapse=" ")
# Chunk could exceed print margin in case the right hand neighbor
# wasn't a blank >> check again
if (nchar(chunk) > print.margin) {
chunk <- makePretty(string=chunk, print.margin=print.margin)
envir$queue <- chunk[length(chunk)]
chunk <- chunk[-length(chunk)]
} else {
if (!is.na(envir$queue)) {
# Prepend chunk with queued chunk
chunk <- paste(envir$queue, chunk, sep=" ")
# Reset queue
envir$queue <- NA
}
}
# /
out <- chunk
return(out)
}))
}
return(out)
}
功能应用
string <- "This is just an example of a very long character string that exceeds the default print margin of 80 and therefore needs some pretty printing. In fact it's so long that it needs to be broken down into three parts."
> makePretty(string=string)
[1] "This is just an example of a very long character string that exceeds the default"
[2] "print margin of 80 and therefore needs some pretty printing. In fact it's so"
[3] "long that it needs to be broken down into three parts."
> string <- "This is just an example of a very long character string that exceeds a certain print margin and therefore needs some pretty printing. In fact it's so long that it needs to be broken down into numerous parts."
> makePretty(string=string, print.margin=40)
[1] "This is just an example of a very long"
[2] "character string that exceeds a certain"
[3] "print margin and therefore needs some"
[4] "pretty printing. In fact it's so long"
[5] "that it needs to be broken down into numerous"
[6] "parts."
string <- "This is just an example of a very long character string that exceeds the default print margin of 80 and therefore needs some pretty printing. In fact it's so looooooooooooooooooooooooooooooooong that it needs to be broken down into four parts."
> makePretty(string=string)
[1] "This is just an example of a very long character string that exceeds the default"
[2] "print margin of 80 and therefore needs some pretty printing. In fact it's so"
[3] "looooooooooooooooooooooooooooooooong that it needs to be broken down into four"
[4] "parts."
string <- "This is just an example of a very long character string that exceeds the default print margin of 80 and therefore needs some pretty printing. In fact it's soooooooo looooooooooooooooooooooooooooooooong that it needs to be broken down into four parts."
> makePretty(string=string)
[1] "This is just an example of a very long character string that exceeds the default"
[2] "print margin of 80 and therefore needs some pretty printing. In fact it's"
[3] "soooooooo looooooooooooooooooooooooooooooooong that it needs to be broken down"
[4] "into four parts."
到目前为止，该方法仅依靠空格来确定哪些词属于一起——这可能不涵盖其他“现实世界场景”，例如冒号、分号等。