Example of named argument not working (as I'd expect) in magrittr

Console Output

> mytestfunction(iris)
Functional sequence with the following components:

 1. data.table(.)
 2. {    if (y)         rbind(head(., 1), tail(., 1))    else .}

Use 'functions' to extract the individual functions. 
> sessionInfo()
R version 3.1.2 (2014-10-31)
Platform: x86_64-w64-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United Kingdom.1252  LC_CTYPE=English_United Kingdom.1252    LC_MONETARY=English_United Kingdom.1252
[4] LC_NUMERIC=C                            LC_TIME=English_United Kingdom.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] data.table_1.9.4 magrittr_1.5    

loaded via a namespace (and not attached):
[1] chron_2.3-45   plyr_1.8.1     Rcpp_0.11.4    reshape2_1.4.1 stringr_0.6.2  tools_3.1.2   

probablyMeNotReadingDocs

library(magrittr)
library(data.table)

mytestfunction<-function(x,y = TRUE) {
  x %>% 
    data.table %>%
{ 
  if(y) {
    .[1:50]
  } else {
    .[1:75]
  } 
} %>%
  nrow
}
mytestfunction(iris)

library(magrittr)
library(data.table)

mytestfunction(x,y = TRUE) {
  x %>%
    data.table %>%
    { 
       if(y) {
          .[1:50]
       } else {
          .[1:75]
       } 
    } %>%
    nrow
  }

mytestfunction(iris)

Would this work? On phone, so excuse typos :)

Ah - so you have to fully name the argument at the beginning of the pipe instead of it allowing the first NULL to receive the value

The first NULL? What should the dot refer to? I am not sure I get what you want? What is the purpose of x in your (original) version?