```
identical(1, NULL) ## FALSE -- don't try this with ==
identical(1, 1.) ## TRUE in R (both are stored as doubles)
identical(1, as.integer(1)) ## FALSE, stored as different types
x <- 1.0; y <- 0.99999999999
## how to test for object equality allowing for numeric fuzz :
(E <- all.equal(x, y))
isTRUE(E) # which is simply defined to just use
identical(TRUE, E)
## If all.equal thinks the objects are different, it returns a
## character string, and the above expression evaluates to FALSE
## even for unusual R objects :
identical(.GlobalEnv, environment())
### ------- Pickyness Flags : -----------------------------
## the infamous example:
identical(0., -0.) # TRUE, i.e. not differentiated
identical(0., -0., num.eq = FALSE)
## similar:
identical(NaN, -NaN) # TRUE
identical(NaN, -NaN, single.NA = FALSE) # differ on bit-level
### For functions ("closure"s): ----------------------------------------------
### ~~~~~~~~~
f <- function(x) x
f
g <- compiler::cmpfun(f)
g
identical(f, g) # TRUE, as bytecode is ignored by default
identical(f, g, ignore.bytecode=FALSE) # FALSE: bytecode differs
## GLM families contain several functions, some of which share an environment:
p1 <- poisson() ; p2 <- poisson()
identical(p1, p2) # FALSE
identical(p1, p2, ignore.environment=TRUE) # TRUE
## in interactive use, the 'keep.source' option is typically true:
op <- options(keep.source = TRUE) # and so, these have differing "srcref" :
f1 <- function() {}
f2 <- function() {}
identical(f1,f2)# ignore.srcref= TRUE : TRUE
identical(f1,f2, ignore.srcref=FALSE)# FALSE
options(op) # revert to previous state
```

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