st: a function to sum variables observation by observation

[Alexander Shevchenko <xanderx@mail.ru>]

Hello
I am wondering is there a function in STATA that generates a sum of variables observation by observation. The one that produces same as ".gen var=var1+var2", however I need to produce a sum of a thousand variables, all of which are called var1 - var1000. 
Any sugestions?
Thank you very much
Alex
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