[R-sig-Geo] spatstat - user-supplied list of point patterns in envelope() error

[Joe Lewis]

Dear list,

I'm trying to use a user-supplied list of point patterns in envelope()
rather than test against the CSR. Page 400 of Spatial Point Patterns:
Methodology and Applications in R states that "the argument simulate
can be a list of point patterns". However, I get the following error
when I try  to supply a list of ppp:

 ekls <- envelope.lpp(Y =  xx, fun = linearK, nsim=5, simulate = pp_list)
Error in envelopeEngine(X = X, fun = fun, simul = simrecipe, nsim = nsim,  :
  ‘simulate’ should be an expression, or a list of point patterns

for reference,

xx
Point pattern on linear network
680 points
Linear network with 22 vertices and 21 lines
Enclosing window: rectangle = [284086.69, 309740] x [709900, 726547.7] metres

class(xx)
[1] "lpp" "ppx"

pp_list
List of point patterns

Component 1:
Planar point pattern: 513 points
window: rectangle = [284086.69, 309740] x [709900, 726547.7] metres

Component 2:
Planar point pattern: 422 points
window: rectangle = [284086.69, 309740] x [709900, 726547.7] metres

Component 3:
Planar point pattern: 495 points
window: rectangle = [284086.69, 309740] x [709900, 726547.7] metres

Component 4:
Planar point pattern: 557 points
window: rectangle = [284086.69, 309740] x [709900, 726547.7] metres

Component 5:
Planar point pattern: 576 points
window: rectangle = [284086.69, 309740] x [709900, 726547.7] metres

class(pp_list)
[1] "ppplist" "solist"  "anylist" "listof"  "list"

Any ideas why the error is occurring? Thanks.