How to resolve the algorithm Remove lines from a file step by step in the Nim programming language

Published on 12 May 2024 09:40 PM
#Nim

How to resolve the algorithm Remove lines from a file step by step in the Nim programming language

Table of Contents

Problem Statement

Remove a specific line or a number of lines from a file. This should be implemented as a routine that takes three parameters (filename, starting line, and the number of lines to be removed). For the purpose of this task, line numbers and the number of lines start at one, so to remove the first two lines from the file foobar.txt, the parameters should be: foobar.txt, 1, 2 Empty lines are considered and should still be counted, and if the specified line is empty, it should still be removed. An appropriate message should appear if an attempt is made to remove lines beyond the end of the file.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Remove lines from a file step by step in the Nim programming language

Source code in the nim programming language

import sequtils, strutils

proc removeLines*(filename: string; start, count: Positive) =

  # Read the whole file, split into lines but keep the ends of line.
  var lines = filename.readFile().splitLines(keepEol = true)

  # Remove final empty string if any.
  if lines[^1].len == 0: lines.setLen(lines.len - 1)

  # Compute indices and check validity.
  let first = start - 1
  let last = first + count - 1
  if last >= lines.len:
    raise newException(IOError, "trying to delete lines after end of file.")

  # Delete the lines and write the file.
  lines.delete(first, last)
  filename.writeFile(lines.join())

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