[Rd] Trying to understand the search path and namespaces

[Hadley Wickham]

Hi all,

I'm trying to understand how the search path and namespaces interact.
For example, take the devtools package which suggests the testthat
package.  Here's what the search path looks like after I load each of
those packages:

> library(devtools)
> search()
 [1] ".GlobalEnv"        "package:devtools"  "package:stats"
 [4] "package:graphics"  "package:grDevices" "package:utils"
 [7] "package:datasets"  "package:methods"   "Autoloads"
[10] "package:base"
> library(testthat)
> search()
 [1] ".GlobalEnv"        "package:testthat"  "package:devtools"
 [4] "package:stats"     "package:graphics"  "package:grDevices"
 [7] "package:utils"     "package:datasets"  "package:methods"
[10] "Autoloads"         "package:base"

My question is this: when I execute the test function in devtools
function it calls the the test_package function in the testthat
package - but that function is located higher up the search path - how
does R find it?

(I ask this question because I'm trying to simulate package loading
from within R to simplify the development cycle, but something is
missing in my knowledge of namespaces, and so I have the devel
versions of my packages can't access packages that are loaded after
they are)

Hadley

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/