gistfile1.txt

> library(purrr)
> ll <- list(list(a=1:3, b=4), list(a=5:7, b=8))
> ll %>% map(lift_dl(c)) %>% map_call(rbind)
     a1 a2 a3 b
[1,]  1  2  3 4
[2,]  5  6  7 8
> Reduce(rbind, ll)
     a         b
init Integer,3 4
     Integer,3 8