[R] debug on lapply

[Duncan Murdoch]

On 11/12/2012 1:17 PM, Asis Hallab wrote:
> Dear R experts,
>
> recently I tried to debug a R function with an internal lapply call.
> When debugging I seem not to be able to use the "n" command to debug the
> inner function called by lapply.
> How could I achieve this?

Jim gave you one solution.  Another is to debug lapply, and when 
stepping through it, debug(FUN) after it is created on the first line.  
Jim's method is more convenient if you are particularly interested in a 
complicated function, this method is better if you are already in the 
middle of debugging and just want to look at a possibly anonymous 
function being passed to lapply.

Duncan Murdoch
>
> *For example:*
> test <- function( ) {
>    lapply( 1:3, function( x ) x + 1 )
> }
> debug( test )
>
> *Start debug:*
> > test()
> debugging in: test()
> debug bei #1:{
>      lapply(1:10, function(x) x + 1)
> }
> Browse[2]> n
> debug bei #2:lapply(1:10, function(x) x + 1)
>
> *The next "n" does not allow me to inspect the inner function,*
> *but gives me the result directly:*
> Browse[2]> n
> exiting from: test()
> [[1]]
> [1] 2
>
> [[2]]
> [1] 3
>
> [[3]]
> [1] 4
>
> Can anyone help me, please?
> Kind regards!
>
> 	[[alternative HTML version deleted]]
>
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