brodieG

list(system=c("browser",
"device",
"dvipscmd",
"mailer",
"pager",
"pdfviewer",
"pkgType",
"printcmd",
"HTTPUserAgent",
"texi2dvi",

brodieG

# Packages

library(devtools)
install_github("smbache/ensurer")
install_github("brodieg/alike")
library(ensurer)
library(alike)
library(magrittr)
set.seed(1)

brodieG

DT[
  id %in% 200:300,
  .(reg.val = sum(value)),
  by=region
][
  reg.val > 0,
  range(reg.val)
]

brodieG

# Because there is no way to tell data.table 
# "interpret this variable as a column name", it's possible to come up
# with corner cases.  I'll grant these are unlikely to occur in day
# to day use, but any function that uses `data.table` must account for
# them

# Low odds, and yes, there are workarounds, but this is
# what I mean by you have to think carefully to avoid 
# corner cases

brodieG

library(devtools)

install_github("pckgA", "brodieg")  # defines old class "file" and class union "fileOrNULL" == c("file", "NULL")
install_github("pckgB", "brodieg")  # defines old class "file", and nothing else

library(pckgA)
makeDummy()          # from pckgA, instantiates a class with a "fileOrNULL" slot, placing a temp file S3 object in the slot
library(pckgB)
makeDummy()          # this fails now