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Can anyone explain why in the following Grid expression the Row expressions are not evaluated ... 

Grid[{{Row[1, " a"], Row[2, " b"]}, {Row[3, " c"], Row[4, " d"]}}, 
      Dividers -> All]

enter image description here

... but when I do it this way they are? 

row = (Row@{##}) &;
Grid[{{row[1, " a"], row[2, " b"]}, {row[3, " c"], row[4, " d"]}}, 
      Dividers -> All]

enter image description here

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The answer is hidden in your question. The construction Row@{##}& works because Row takes a vector/list of expressions as input and with the {} you have defined such a vector! Try Row[{1,"a"}] will also work similar fashion. – PlatoManiac Oct 22 '12 at 18:39

closed as too localized by Mr.Wizard♦ Oct 22 '12 at 18:49

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1 Answer

up vote 1 down vote accepted

Row[] takes a list as the argument.

In your first case, you failed to provide a list.

While in your second case:

row = (Row@{##}) &;
Grid[{{row[1, " a"], row[2, " b"]}, {row[3, " c"], row[4, " d"]}}] // FullForm

(*  
Grid[List[List[Row[List[1," a"]],Row[List[2," b"]]],
          List[Row[List[3," c"]],Row[List[4," d"]]]]]
*)
share|improve this answer
Of course -- how stupid of me. – m_goldberg Oct 22 '12 at 18:47
@m_goldberg I'll not throw the first stone :) – belisarius Oct 22 '12 at 18:51

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