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Comment by tracker1 | Hacker News Reader

I'd probably reach for node.js for something like this...

    var fs = require('fs');
    var lines = fs.readFileSync('./somefile.txt','utf8')
      .trim().split(/\r\n|\r|\n/g);
    for (var i=0; i<lines.length; i++) {
      lines[i] = i * +lines[i];
    }
    fs.writeFileSync(
      './outfile.txt'
      ,'urf8'
      ,lines.join('\n')
    );

Easy peasy. That's off the top of my head so fs syntax may not be correct. I'd probably give it a quick run through in the node repl to start with.

Why JS, I find that this type of scenario begs for a language that does coercion well... say what you will about JS, it does do that.

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Really, that's easy peasy? Looks terrible to a Python programmer. :-)

   with open('input') as fin, open('output', 'w') as fout:
       for line_num, line in enumerate(fin, 1):
           fout.write('{0}\n'.format(int(line) * line_num))

I would've went with Haskell myself ;)

    main :: IO ()
    main = writeListAsLines . toDoubleList . lines =<< readFile "nums.txt"
           where
             toDoubleList y = zipWith (*) (map read y) [1..length y]
             writeListAsLines z =  writeFile "output.txt" (concat $ intersperse "\n" $ map show z)

I think you would really enjoy learning some other languages. You obviously understand programming concepts really well... but, node.js for this? really? Even C is less verbose than that JS...:

    #include <stdio.h>
    int main(void){
        unsigned int lineno=0;
        char line[1000];
        unsigned int number;

        while (fgets(line, 999, stdin)) {
            sscanf(line, "%u", &number);
            printf("%u\n", number * lineno++);
        }
        return(0);
    }

which reads stdin, and writes to stdout.

I'm sure the C may not be perfect, I've not really used it in years. Node for a task like this is a bit like using a Nimitz Class Aircraft Carrier to hammer in a nail...

stdin/out for node.js

    var i=0
        ,stream = require("stream")
        ,rl = require('readline').createInterface({
            input: process.stdin
            ,output: new stream.Writable() 
        });
    rl.on('line',function(line){
        process.stdout.write(((+line || 0) * ++i) + '\n');
    });
    process.stdin.resume();

I actually know several languages... ;-) Just find that node is my go to tool these days.

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