Remove a subset from a global - Stata

* This program will remove from a global a set of specified values
* I believe this is the same in sigma algebra of subtracting a set from another
* I figure there is probably a prewritten command for this but I have not been able to find it.

cap program drop takefromglobal
program define takefromglobal
 
  * First define a local called temp to hold the initial values of the global
  local temp ${`1'}
 
  * Empty the global
  global `1'
 
  * Loop through each of the old values
  foreach v of local temp {
   
* Start counting at 0
    local i = 0

* Create a local that indicates that this value should be skipped (initially assume no skipping)
local skip = 0

* Loop through all of the user specified inputs `0'
    foreach vv in `0' {

* We will skip the first one since we know it is just the global specified
      local i = `i' + 1

 * If we are past the first input in the local and one our values to exclude matches the value in the global skip that value
 if `i' > 1 & "`vv'"=="`v'" local skip = 1
    }

* If the current value is not to be skipped then add it to the new global list
if `skip' == 0 global `1' ${`1'} `v'
  }
end

global XYZ a b c d e f g a b c d e

di "$XYZ"

takefromglobal XYZ a b c

di "$XYZ"