st: Modifying the content of a macro

[Thomas Speidel <thomas@tmbx.com>]

I am writing a loop to cycle through a number of models. For example,

. sysuse auto
(1978 Automobile Data)

. local main mpg price weight

. local adjust length gear_ratio turn

. foreach c of local main {
  2. local nolength: list adjust - "length"
  3. logistic foreign `c' `adjust' if "`c'" != "weight"
  4. logistic foreign `c' `nolength' if "`c'" == "weight"
  5. }

Which fails on the second model.  How do I modify `adjust' so that the  
string "length" is removed from its content and applied to the second  
set of models? In a less automated fashion, I want:

. logistic foreign mpg length gear_ratio turn
. logistic foreign price length gear_ratio turn
. logistic foreign weight gear_ratio turn

Preferrably, in this order.  Creating another macro without "length"  
is not ideal, because I am dealing with a much larger set of covariates.
Thanks.

--
Thomas Speidel

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