How to resolve the algorithm Read a file line by line step by step in the J programming language

Published on 12 May 2024 09:40 PM
#J

How to resolve the algorithm Read a file line by line step by step in the J programming language

Table of Contents

Problem Statement

Read a file one line at a time, as opposed to reading the entire file at once.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Read a file line by line step by step in the J programming language

Source code in the j programming language

cocurrent 'linereader'

  NB. configuration parameter
  blocksize=: 400000

  NB. implementation
  offset=: 0
  position=: 0
  buffer=: ''
  lines=: ''

  create=: monad define
    name=: boxxopen y
    size=: 1!:4 name
    blocks=: 2 <@(-~/\)\ ~. size <. blocksize * i. 1 + >. size % blocksize
  )

  readblocks=: monad define
     if. 0=#blocks do. return. end.
     if. 1<#lines do. return. end.
     whilst. -.LF e.chars do.
       buffer=: buffer,chars=. 1!:11 name,{.blocks
       blocks=: }.blocks
       lines=: <;._2 buffer,LF
     end.
     buffer=: _1{::lines
  )

  next=: monad define
    if. (#blocks)*.2>#lines do. readblocks'' end.
    r=. 0{::lines
    lines=: }.lines
    r
  )


   example=: '/tmp/example.txt' conew 'linereader'
   next__example''
this is line 1
   next__example''
and this is line 2

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