I have two lists, L1 and L2, each with a key and some data. Let us say the key is a person's name, a string, and the data follows:

L1 = {
       {"Joseph O'Rourke", data1, data2, ... },
       ...
     }

I would like to "align" the two lists in the following sense. If L1 has a name A that is not in L2, then L2 is padded to include a "blank" record for A. And vice versa: If L2 has a name B that is not in L1, then L1 is modified to include a "blank" record for B. Then I will have two lists that "align":

L1' = { {A,...}, {0,...}, {C,...},  {D,...}, ...}
L2' = { {A,...}, {B,...}, {0,...},  {D,...}, ...}

where maybe 0 == {}. With the lists aligned in this fashion, I could make a two-column table (one column per list) that would directly compare one list against the other. My question is:

What is a clean method for accepting L1 and L2 as input, and returning L1' and L2' as output, with the latter two lists aligned as above?

I can accomplish this via tedious list For-loops, but I suspect the cognoscenti :-) will offer more concise and efficient methods. Thanks for your help!

I have two lists, L1 and L2, each with a key and some data. Let us say the key is a person's name, a string, and the data follows. (To respond to rasher's query:) Let us also assume the lists are sorted by key:

L1 = {
       {"Joseph O'Rourke", data1, data2, ... },
       ...
     }

I would like to "align" the two lists in the following sense. If L1 has a name A that is not in L2, then L2 is padded to include a "blank" record for A. And vice versa: If L2 has a name B that is not in L1, then L1 is modified to include a "blank" record for B. Then I will have two lists that "align":

L1' = { {A,...}, {0,...}, {C,...},  {D,...}, ...}
L2' = { {A,...}, {B,...}, {0,...},  {D,...}, ...}

where maybe 0 == {}. With the lists aligned in this fashion, I could make a two-column table (one column per list) that would directly compare one list against the other. My question is:

What is a clean method for accepting L1 and L2 as input, and returning L1' and L2' as output, with the latter two lists aligned as above?

I can accomplish this via tedious list For-loops, but I suspect the cognoscenti :-) will offer more concise and efficient methods. Thanks for your help!

I have two lists, L1 and L2, each with a key and some data. Let us say the key is a person's name, a string, and the data follows:

L1 = {
       {"Joseph O'Rourke", data1, data2, ... },
       ...
     }

I would like to "align" the two lists in the following sense. If L1 has a name A that is not in L2, then L2 is padded to include a "blank" record for A. And vice versa: If L2 has a name B that is not in L1, then L1 is modified to include a "blank" record for B. Then I will have two lists that "align":

L1' = { {A,...}, {0,...}, {C,...},  {D,...}, ...}
L2' = { {A,...}, {B,...}, {0,...},  {D,...}, ...}

where maybe 0 == {}. My question is:

What is a clean method for accepting L1 and L2 as input, and returning L1' and L2' as output, with the latter two lists aligned as above?

I can accomplish this via tedious list For-loops, but I suspect the cognoscenti will offer more concise and efficient methods. Thanks for your help!

I have two lists, L1 and L2, each with a key and some data. Let us say the key is a person's name, a string, and the data follows:

L1 = {
       {"Joseph O'Rourke", data1, data2, ... },
       ...
     }

I would like to "align" the two lists in the following sense. If L1 has a name A that is not in L2, then L2 is padded to include a "blank" record for A. And vice versa: If L2 has a name B that is not in L1, then L1 is modified to include a "blank" record for B. Then I will have two lists that "align":

L1' = { {A,...}, {0,...}, {C,...},  {D,...}, ...}
L2' = { {A,...}, {B,...}, {0,...},  {D,...}, ...}

where maybe 0 == {}. With the lists aligned in this fashion, I could make a two-column table (one column per list) that would directly compare one list against the other. My question is:

What is a clean method for accepting L1 and L2 as input, and returning L1' and L2' as output, with the latter two lists aligned as above?

I can accomplish this via tedious list For-loops, but I suspect the cognoscenti :-) will offer more concise and efficient methods. Thanks for your help!