Flatten deeply nested list of dataframes

Consider this nested list of dataframes:

df <- data.frame(x = 1:5, y = letters[1:5])
l <- list(df, list(df, df), list(df, list(df, df, list(df))), list(df), df)

How can one get from this deeply nested list to a simple list of dataframes:

list(df, df, df, df, df, df, df, df, df)

Usual solutions (like here) fails to keep dataframes’ structure.

>Solution :

A convenient option is to use rrapply:

rrapply(l, classes = "data.frame", how = "flatten")

Check whether it’s the same as the desired output:

identical(list(df, df, df, df, df, df, df, df, df), 
          rrapply(l, classes = "data.frame", how = "flatten"))

[1] TRUE