R devel - Nov 1997 - R-alpha: "invisible" (yet again): a more problematic bug[let]

I think this is a more problematic buglet
in (implicit/explicit)  ``invisible behavior'').

Try this  (all versions of R from  0.49 to 0.60):


test0 <- function() c(1,2)
test  <- function(two = FALSE)        c(1, if(two) 2)
testR <- function(two = FALSE) return(c(1, if(two) 2))

test0()# 1 2 as it should
test() #
<<<<<<<<<<<<<<<<<<<<<<
INVISIBLE! @#$@!
test(T)# 1 2
print(test())
print(test(T))

testR() # ok; NOT invisible...
testR(T)# 1 2

---------------------------
Even though it is not really harmful once you know about it,
it can be pretty wierd when you try and test functions...

-- Martin
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maechler@stat.math.ethz.ch wrote:
> 
> Try this  (all versions of R from  0.49 to 0.60):
> 
> test0 <- function() c(1,2)
> test  <- function(two = FALSE)        c(1, if(two) 2)
> testR <- function(two = FALSE) return(c(1, if(two) 2))
> 
> test0()# 1 2 as it should
> test() #
<<<<<<<<<<<<<<<<<<<<<<
INVISIBLE! @#$@!
> test(T)# 1 2
> print(test())
> print(test(T))
> 
> testR() # ok; NOT invisible...
> testR(T)# 1 2
The problem seems to be in do_if (eval.c) where the R_Visible flag
is set to 0. Set it to 1 instead and your functions will work
properly. You also get

R>if(F) 2
NULL

instead of 
R>if(F) 2
R>

which is consistent with S-PLUS.

Martyn
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