读取Clojure中的文件并忽略第一行? [英] Read a file in clojure and ignore the first line?

问题描述

使用此答案中的代码，我有

(defn repeat-image [n string]
  (println (apply str (repeat n string))))

(defn tile-image-across [x filename]
  (with-open [rdr (reader filename)]
    (doseq [line (line-seq rdr)]
      (repeat-image x line))))

...以水平平铺ascii图像.现在，我将如何忽略"第一行?我这样做的原因是每个图像的第一行都具有坐标(例如"20 63")，而我不需要该行.我尝试了一些方法(保持索引，模式匹配)，但是我的方法感觉很虚构.

...to tile an ascii image horizontally. Now, how would I be able to "ignore" the first line? The reason I'm doing this is each image has the coordinates (for example "20 63") as the first line, and I don't need the line. I tried some ways (keeping an index, pattern matching) but my approaches felt contrived.

推荐答案

假设您要跳过文件的第一行，并像在 tile-image-across 中一样处理其余行>，您只需将(line-seq rdr)替换为

Assuming you'd like to skip the first line of the file and process the remaining lines as you do in tile-image-across, you can simply replace (line-seq rdr) with

(next (line-seq rdr))

实际上，您可能应该排除选择相关行和处理的可能性:

In fact, you should probably factor out selecting the relevant lines and the processing:

;; rename repeat-image to repeat-line

(defn read-image [rdr]
  (next (line-seq rdr)))

(defn repeat-image! [n lines]
  (doseq [line lines]
    (repeat-line n line)))

在 with-open 内部使用:

(with-open [rdr ...]
  (repeat-image! (read-image rdr)))

如果相反，您的文件包含多个图像，而您需要跳过每个图像的第一行，则最好的方法是编写一个函数，将行的序列划分为一系列的图像(具体操作取决于文件格式)，然后将其映射到(行序列rdr)和(映射下一个...))的结果上:

If instead your file holds multiple images and you need to skip the first line of each, the best way would be to write a function to partition the seq of lines into a seq of images (how that'd be done depends on the format of your file), then map that over (line-seq rdr) and (map next ...)) over the result:

(->> (line-seq rdr)
     ;; should partition the above into a seq of seqs of lines, each
     ;; describing a single image:
     (partition-into-individual-image-descriptions)
     (map next))

NB.带有<懒惰的 partition-into-individual-image-descriptions ，这将产生一个懒惰的seq懒惰序列.您需要先消耗它们，然后 with-open 关闭阅读器.

NB. with a lazy partition-into-individual-image-descriptions this will produce a lazy seq of lazy seqs; you'll need to consume them before with-open closes the reader.

这篇关于读取Clojure中的文件并忽略第一行?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！