Boris Steipe
2020-Nov-09 11:38 UTC
[R] paste() turns list element character vector into deparsed expression. Why?
I was just surprised by very un-intuitive behaviour of paste(), which appears to collapse a one-column data frame or one-element list into a deparsed expression, rather than producing the expected string. Can someone kindly explain what's going on here? reprex: ====== list(s = c("xyz", "uvw")) # s # 1 xyz # 2 uvw paste(list(s = c("xyz", "uvw")), collapse = "") # [1] "c(\"xyz\", \"uvw\")" # This is unexpected! I would have expected: # [1] "xyzuvw" ... which I do get with e.g. paste(list(s = c("xyz", "uvw"))$s, collapse = "") But what logic is there in returning a deparsed expression? Thanks! Boris
Ege Rubak
2020-Nov-09 12:24 UTC
[R] paste() turns list element character vector into deparsed expression. Why?
I think `paste()` just calls `as.character()` on each input argument and then collapses things afterwards. Calling `as.character()` on the first input argument generates exactly the output you show (and didn't expect) and there is nothing to collapse. So changing `collapse = ""` to anything else doesn't change behaviour. The question is reduced to how `as.character()` should handle a list as input. It seems to me that this input is so generic that it is hard to handle graciously without all kinds of special cases. So you expect the length one list as.character(list(s = c("xyz", "uvw")) to return the length 2 character vector `c("xyz", "uvw")`? What should as.character(list(s = c("xyz", "uvw"), t = c("a", "b", "c")) return? Kind regards, Ege On Mon, 2020-11-09 at 11:38 +0000, Boris Steipe wrote:> I was just surprised by very un-intuitive behaviour of paste(), which > appears to collapse a one-column data frame or one-element list into > a deparsed expression, rather than producing the expected string. Can > someone kindly explain what's going on here? > > > reprex: > ======> > list(s = c("xyz", "uvw")) > # s > # 1 xyz > # 2 uvw > > paste(list(s = c("xyz", "uvw")), collapse = "") > # [1] "c(\"xyz\", \"uvw\")" # This is unexpected! > > I would have expected: > # [1] "xyzuvw" > > ... which I do get with e.g. > paste(list(s = c("xyz", "uvw"))$s, collapse = "") > > But what logic is there in returning a deparsed expression? > > > > Thanks! > Boris > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.
Boris Steipe
2020-Nov-09 12:58 UTC
[R] paste() turns list element character vector into deparsed expression. Why?
Thanks Ege - That narrows it down, ... but it's still weird. My issue is that I don't consider "c(\"xyz\", \"uvw\")" to be a valid character representation of a list. c() is a function, so "c(\"xyz\", \"uvw\")" is a string representation of a function call that could be eval(parse(...))'ed into a two-element vector ... but considering this a coercion seems really weird. What do I think your example should return? An object of the same general structure as the input, with non-character components coerced to character. And if that's not possible because there is no good character representation (e.g. if its a closure) than it should return an error. Cheers, Boris> On 2020-11-09, at 22:24, Ege Rubak <rubak at math.aau.dk> wrote: > > EXTERNAL EMAIL: Treat content with extra caution. > > I think `paste()` just calls `as.character()` on each input argument > and then collapses things afterwards. Calling `as.character()` on the > first input argument generates exactly the output you show (and didn't > expect) and there is nothing to collapse. So changing `collapse = ""` > to anything else doesn't change behaviour. > > The question is reduced to how `as.character()` should handle a list as > input. It seems to me that this input is so generic that it is hard to > handle graciously without all kinds of special cases. So you expect the > length one list > > as.character(list(s = c("xyz", "uvw")) > > to return the length 2 character vector `c("xyz", "uvw")`? What should > > as.character(list(s = c("xyz", "uvw"), t = c("a", "b", "c")) > > return? > > Kind regards, > Ege > > On Mon, 2020-11-09 at 11:38 +0000, Boris Steipe wrote: >> I was just surprised by very un-intuitive behaviour of paste(), which >> appears to collapse a one-column data frame or one-element list into >> a deparsed expression, rather than producing the expected string. Can >> someone kindly explain what's going on here? >> >> >> reprex: >> ======>> >> list(s = c("xyz", "uvw")) >> # s >> # 1 xyz >> # 2 uvw >> >> paste(list(s = c("xyz", "uvw")), collapse = "") >> # [1] "c(\"xyz\", \"uvw\")" # This is unexpected! >> >> I would have expected: >> # [1] "xyzuvw" >> >> ... which I do get with e.g. >> paste(list(s = c("xyz", "uvw"))$s, collapse = "") >> >> But what logic is there in returning a deparsed expression? >> >> >> >> Thanks! >> Boris >> ______________________________________________ >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code.