Thanks!  So $v, $x, $y, and $z should always get a "--" before them -- 
that's sufficient logic to do it 'right'?  I guess an LCSH 6xx always 
needs an $a first, so I don't need to worry about if a $v or $x happens 
to come first, and shouldn't get a preceding "--".

Should I do this only for 6xx with 2nd indicator 2 indicating LCSH, or 
do people generally just do this for all 6xx?

Tod Olson wrote:
> Only for certain subfields:
>
> Dash (-) that precedes a subdivision in an extended 600 subject  
> heading is not carried in the MARC record. It may be system generated  
> as a display constant associated with the content of subfield $v, $x,  
> $y, and $z.
>
>  From http://www.loc.gov/marc/bibliographic/bd600.html
>
> -Tod
>
> On Sep 23, 2009, at 9:09 AM, Jonathan Rochkind wrote:
>
>   
>> Hi all, I'm writing some marc record display code, and I have a  
>> question about the 'right' way to display LCSH headings.
>>
>> LCSH headings are typically displayed with "--" between components.  
>> But looking at the MARC, it looks like the "--" punctuation isn't  
>> actually in the MARC field. (A rare instance where display  
>> punctuation isn't in the marc!).
>>
>> Is it correct for any LCSH 6xx field (which you know because the 2nd  
>> indicator is 0, right?), to add "--" between ALL present subfields  
>> on display?   Do I have the right logic there?
>>
>> Thanks for any advice!
>>
>> Jonathan
>>     
>
>