Aggregate multidimensional array

Question

Trying to modularise some latex table generation code, massive gold plating.

var MIDRULE = @"\\\midrule";

var a = new []{new []{"a", "b", "c"}, new []{"1", "2", "3"}, new []{"alpha", "beta", "gamma"}};

a.Dump();

a.Aggregate(
        (x,y) => x.Aggregate((i,j) => i + "&" + j) 
           + MIDRULE + Environment.NewLine
           + y.Aggregate((k,l)=>k+"&"+l)).Dump();

Expected result:

a&b&c\\\midrule
1&2&3\\\midrule
alpha&beta&gamma\\\midrule

Actual result:

Cannot implicitly convert type 'string' to 'string[]'

I'd like to do this with a one liner of aggregate commands if possible, can already do this in a nested loop or various other ways, I'm interested in getting to know aggregation better.

Ani · Accepted Answer · 2012-10-02 04:00:56Z

3

Try:

string.Concat(a.Select(inner => string.Join("&", inner)
                                + MIDRULE + Environment.NewLine))
      .Dump();

Be careful not to use Join for the outer call as you want MIDRULE + Environment.NewLine to be appended to every string including the last one.

Edit:

Since you are keen to use Aggregate here (I wouldn't recommend it as it is less readable and much more inefficient), try (untested):

a.Aggregate(string.Empty, (x, y) => x 
                                  + y.Aggregate(string.Empty,
                                                (k, l) => k + "&" + l) 
                                  + MIDRULE 
                                  + Environment.NewLine)
 .Dump();

edited Oct 2, 2012 at 4:00

answered Oct 2, 2012 at 2:43

Ani

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2 Comments

Joe Over a year ago

Thanks for this simple way, I would have liked to see if it was possible just using aggregate though... looks more readable to me

Ani Over a year ago

I added a way with Aggregate. I wouldn't go down that route if I were you.

Craig Suchanec · Accepted Answer · 2012-10-02 03:00:56Z

1

Its because you are using Aggregate wrong. If you look at the definition of Aggregate you will see the definition is:

public static TSource Aggregate<TSource>(
    this IEnumerable<TSource> source,
    Func<TSource, TSource, TSource> func
)

You notice that the generic only takes one type so you are implicitly calling Aggregate which means the parameters to the function all have to be string[]. When you try to use a type string as the parameters and the expected output the compile error occurs.

Off the top of my head one way to do this would be

string.Join( MIDRULE + Environment.NewLine, a.Select(x => string.Join( "&", x))).Dump();

If you didn't want the trailing MIDRULE Newline and the already recommended

I'm not sure if this is the best way to approach this but it should work.

string.Concat(a.Select(inner => string.Join("&", inner)
                            + MIDRULE + Environment.NewLine))
  .Dump();

If you did.

answered Oct 2, 2012 at 3:00

Craig Suchanec

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1 Comment

Joe Over a year ago

Thanks for the extra info, i realised that I had worded the expected results wrong, you're right that I didn't want the trailing MIDRULE but i think it'd be unfair to mark this the correct answer since Ani's earlier answer outputted my (incorrect) expected results.

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