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setMethodS3("wstring", "default", function(..., sep="", envir=parent.frame()) {
s <- paste(..., sep=sep)
# Nothing to do?
if (length(s) == 0L) return(s)
if (length(s) > 1L) {
Recall <- sys.function(); # base::Recall() does not work with *apply()
return(sapply(s, FUN=Recall, envir=envir))
}
# Nothing to do?
if (regexpr("{{", s, fixed=TRUE) == -1L) {
return(s)
}
bfr <- NULL
pattern <- "{{(.*?)}}"
while ((pos <- regexpr(pattern, s, perl=TRUE)) != -1L) {
# Parse
len <- attr(pos, "match.length")
head <- substring(s, first=1L, last=pos-1L)
code <- substring(s, first=pos+2L, last=pos+len-3L)
s <- substring(s, first=pos+len)
# Evaluate
expr <- base::parse(text=code)
value <- eval(expr, envir = envir, enclos = baseenv())
value <- as.character(value)
bfr <- c(bfr, head, value)
}
bfr <- c(bfr, s)
bfr <- paste(bfr, collapse="")
bfr
}, protected=TRUE) # wstring()
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