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#### GROUP DEFINITION SYNTAX --------------------------------------------------
## USER-FACING
# user-defined variable group:
# Returns a function that expands a call in which a group name is used
# to a list of calls.
#
# name (possibly unqouted) name of the group.
# ...
var_group <- function(...){
L <- as.list(substitute(list(...))[-1])
function(){
if (length(L)==0) return(NULL)
out <- L[[1]]
L <<- L[-1]
out
}
}
## UNDER THE HOOD
# Replace occurrences of 'vargroup(v1,v2,...,vn)'
# calls: 'list' of calls
# output: the same list of calls, but ocurrences of 'vargroup' have been multiplied
#
expand_groups <- function(calls){
L <- list()
for (k in seq_along(calls)){
# this copies the name.
U <- calls[k]
# get reference
ref <- get_ref(U)
# find var groups, if any.
cl <- calls[[k]]
I <- which.call(cl,'var_group')
if (length(I) > 0){
i <- I[[1]]
i <- i[-length(i)]
f <- eval(cl[[i]])
U <- list()
while(!is.null(x <- f())){
u <- cl
u[[i]] <- x
U <- c(U,u)
}
names(U) <- paste0(names(calls)[k],".",seq_along(U))
U <- set_ref(U, rep(ref, length(U)))
}
L <- c(L,U)
}
L <- unlist(L)
# recurse to check if groups are still present.
if (length(L) > length(calls))
expand_groups(L)
else
L
}
#### ASSIGNMENT SUBSTITUTION --------------------------------------------------
## All under the hood
## Substitute assignments in subsequent calls
expand_assignments <- function(calls){
e <- new.env()
i <- 1
lapply(calls, function(x){
x <- substitute_assignments(x,e)
# add index into original list of calls.
attr(x,"reference") <- i
i <<- i+1
if(x[[1]] == ':=')
add_assignment(x,e)
x
}
)[!is.assignment(calls)]
}
substitute_assignments <- function(call,assignments){
for ( lhs in ls(assignments) ){
i <- which.call(call, lhs)
for ( j in i ){
call[[j]] <- assignments[[lhs]]
}
}
call
}
# add named assignment to environment
# - rhs is 'embraced' for substitution
add_assignment <- function(assignment, e){
e[[as.character(left(assignment))]] <- right(assignment)
assignment
}
# check wether a call is an assignment
is.assignment <- function(x) sapply(x,function(y) y[[1]] == ":=")
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