data argument and environments

I'm having difficulty with an environmental issue:  I have an additive  
model fitting function
with a typical call that looks like this:

require(quantreg)
n <- 100
x <- runif(n,0,10)
y <- sin(x) + rnorm(n)/5
d <- data.frame(x,y)
lam <- 2

	f <- rqss(y ~ qss(x, lambda = lam), data = d)

this is fine when invoked as is; x and y are found in d, and lam is  
found the .GlobalEnv,
or at least this is how I understand it.  Now,  I'd like to have a  
function say,

	h <- function(lam)
		AIC(rqss(y ~ qss(x, lambda = lam), data = d))

but now,  if I do:

	rm(lam)
	h(1)
Error in qss1(x, constraint = constraint, lambda = lambda, dummies =  
dummies,  :
   object "lam" not found

worse, if there is a "lam"  in the .GlobalEnv it is used instead of  
the argument specified to h().
If I remove the data=d argument in the function definition then lam is  
passed correctly.
presumably because data defaults to parent.env().   I recognize that  
this is probably an elementary confusion on my part, but my  
understanding of environments is very limited.
I did read  the entry for FAQ 7.12,  but I'm still unenlightened.

data argument and environments

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