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digitalmars.D.learn - naming a variable at runtime

reply "InfinityPlusB" <brian infinityplusb.com> writes:
Hi clever people

I'm trying to do something which I thought would be easy.
Read a file in, and for every row, create a array.

I want to be able to name the rows, as they are built.
So when row 1 is read in I get
int[] bob_1 = new int[0];
when the second row is read in, I get
int[] bob_2 = new int[0];

So at the end of running my program I effectively want bob_1, 
bob_2 and bob_3.
And then I can do something more interesting with them ...

I realise this is now slightly beyond my if-then-else 
capabilities, and was wondering if I could get some direction.

Thanks
B


The contents of /home/bob/test.csv
-1, -1, 1, -1, -1
-1, 1, 1, 1, -1
1, -1, -1, 1, -1

My Program

import std.stdio;
import std.array;
import std.conv;
import std.string;

void main()
{
   string inputFile = "/home/bob/test.csv";
//  string inputFile = "-1, -1, 1, -1, -1\n-1, 1, 1, 1, -1\n1, 
-1, -1, 1, -1\r\n";
   auto readInFile = File(inputFile);
   int count = 0;
   foreach(line; readInFile.byLine())
   {
     int[] bob = new int[0];
// int[] bob_NUMBER_ME = new int[0];
     foreach(item;line.split(","))
     {
       writeln(strip(item));
       bob ~=  to!int(strip(item));
     }
     writeln(bob);
     writefln("Line number %d", count);
     count++;
   }
   writeln("Done");
}
May 12 2014
next sibling parent reply "safety0ff" <safety0ff.dev gmail.com> writes:
You should look into associative arrays ( 
http://dlang.org/hash-map .)

Example:

import std.stdio;

void main()
{
	int[][string] mybobs;
	mybobs["bob_1"] = [-1, -1, 1, -1, -1];
	mybobs["bob_2"] = [-1, 1, 1, 1, -1];
	mybobs["bob_3"] = [-1, 1, 1, 1, -1];
	writeln(mybobs);
}
May 12 2014
parent "InfinityPlusB" <brian infinityplusb.com> writes:
On Tuesday, 13 May 2014 at 03:54:33 UTC, safety0ff wrote:

 You should look into associative arrays ( 
 http://dlang.org/hash-map .)

 Example:

 import std.stdio;

 void main()
 {
 	int[][string] mybobs;
 	mybobs["bob_1"] = [-1, -1, 1, -1, -1];
 	mybobs["bob_2"] = [-1, 1, 1, 1, -1];
 	mybobs["bob_3"] = [-1, 1, 1, 1, -1];
 	writeln(mybobs);
 }


Thanks for the quick reply, I'll look into that.

My issue is (which I didn't explain clearly, sorry) how do I do 
it with an unknown number of lines?
So my example has 3 lines. What if it had 300? or 3000?
Basically so I can run the same piece of code for any size file, 
and it will create a new named array for each line.
So I assume(?) I have to do something that will "name" each of 
these arrays at runtime.

So,
for(x;1 ... n)
   bob_x = ...
May 12 2014
prev sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 05/12/2014 08:47 PM, InfinityPlusB wrote:


 I want to be able to name the rows, as they are built.


First, no, you cannot name variables at run time because variables are 
concepts of source code; they don't exist in the compiled program.


 So when row 1 is read in I get
 int[] bob_1 = new int[0];
 when the second row is read in, I get
 int[] bob_2 = new int[0];


Well, it looks like a bob array. :) How about "naming" those rows as 
bob[0], bob[1], etc.


 So at the end of running my program I effectively want bob_1, bob_2 and
 bob_3.


Would zero-indexing work?


 And then I can do something more interesting with them ...

 I realise this is now slightly beyond my if-then-else capabilities, and
 was wondering if I could get some direction.


I had used the same naming scheme as a segway to my arrays chapter:

   http://ddili.org/ders/d.en/arrays.html


 The contents of /home/bob/test.csv
 -1, -1, 1, -1, -1
 -1, 1, 1, 1, -1
 1, -1, -1, 1, -1

 My Program

 import std.stdio;
 import std.array;
 import std.conv;
 import std.string;

 void main()
 {
    string inputFile = "/home/bob/test.csv";
 //  string inputFile = "-1, -1, 1, -1, -1\n-1, 1, 1, 1, -1\n1, -1, -1,
 1, -1\r\n";
    auto readInFile = File(inputFile);
    int count = 0;
    foreach(line; readInFile.byLine())
    {
      int[] bob = new int[0];
 // int[] bob_NUMBER_ME = new int[0];
      foreach(item;line.split(","))
      {
        writeln(strip(item));
        bob ~=  to!int(strip(item));
      }
      writeln(bob);
      writefln("Line number %d", count);
      count++;
    }
    writeln("Done");
 }


Here is the inner loop with minimal changes to your program:

    int[][] bob;                        // <== Array of arrays

    foreach(line; readInFile.byLine())
    {
        int[] row;                      // <== Make a new row

        foreach(item;line.split(","))
        {
            writeln(strip(item));
            row ~= to!int(strip(item));
        }

        bob ~= row;                     // <== Add the row

      writefln("Line number %d", count);
      count++;
    }
    writeln(bob);

Ali
May 12 2014
parent reply "InfinityPlusB" <brian infinityplusb.com> writes:
On Tuesday, 13 May 2014 at 04:26:04 UTC, Ali Çehreli wrote:

 On 05/12/2014 08:47 PM, InfinityPlusB wrote:


 I want to be able to name the rows, as they are built.


 First, no, you cannot name variables at run time because 
 variables are concepts of source code; they don't exist in the 
 compiled program.


That's good to know, I'll stop trying to make that happen. :P


 Here is the inner loop with minimal changes to your program:

    int[][] bob;                        // <== Array of arrays

    foreach(line; readInFile.byLine())
    {
        int[] row;                      // <== Make a new row


yup, that will work.
If I wasn't hell bent on naming variables, I probably would have 
figured this out. :P

Thanks.
May 12 2014
parent Jacob Carlborg <doob me.com> writes:
On 13/05/14 06:32, InfinityPlusB wrote:


 yup, that will work.
 If I wasn't hell bent on naming variables, I probably would have figured
 this out. :P


Perhaps you could use an associative array. Then you get sort of named 
variables.

-- 
/Jacob Carlborg
May 12 2014