For fun: Expressive C++ 17 Coding Challenge in D

[Ali Çehreli]

On 10/04/2017 02:04 AM, Biotronic wrote:

 > I opted for writing to stdout instead, because 1) it's easier, x) it's
 > less code, and b) it's more flexible.

Exactly! :)

 > a simple replacement of readText with an mmapped equivalent should
 > enable humongous file support with no other code change required.

Here is one from me:

import std.stdio;
import std.algorithm;
import std.string;
import std.range;

const delim = ",";

auto byColumn(R)(R range) {
     return range
            .splitter(delim)
            .map!strip;
}

int main(string[] args) {
     if (args.length != 3) {
         stderr.writefln("USAGE: %s <column-name> <replacement>", args[0]);
         return 1;
     }

     const columnName = args[1];
     auto lines = stdin.byLine;

     const columnNumber = lines
                          .front
                          .byColumn
                          .countUntil(columnName);
     if (columnNumber == -1) {
         stderr.writefln(`ERROR: Failed to find "%s".`, columnName);
         return 1;
     }

     writeln(lines.front);
     lines.popFront();

     const replacement = args[2];
     auto replaced = lines
                     .map!(line => line
                                   .byColumn
                                   .enumerate
                                   .map!(t => (t[0] == columnNumber) ? 
replacement : t[1])
                                   .joiner(delim));

     writefln("%(%s\n%)", replaced);

     return 0;
}

Ali