diff --git a/DESCRIPTION b/DESCRIPTION
index 2da50232b..92b5da3b1 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -59,10 +59,11 @@ Collate:
     'expr__meta.R'
     'expr__string.R'
     'expr__struct.R'
-    'functions.R'
+    'functions__eager.R'
+    'functions__lazy.R'
+    'functions__whenthen.R'
     'groupby.R'
     'ipc.R'
-    'lazy_functions.R'
     'lazyframe__background.R'
     'lazyframe__groupby.R'
     'lazyframe__lazy.R'
@@ -77,7 +78,6 @@ Collate:
     'series__series.R'
     'translation.R'
     'vctrs.R'
-    'whenthen.R'
     'zzz.R'
 Config/rextendr/version: 0.2.0.9000
 VignetteBuilder: knitr
diff --git a/NEWS.md b/NEWS.md
index 392435993..8224b3e5e 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,9 @@
 # polars (development version)
 
+## What's changed
+ - lazy functions translated: `pl$implode`, `pl$explode`, `pl$unique`, `pl$approx_unique`, `pl$head`, `pl$tail` (#196)
+ - `pl$list` is deprecated, use `pl$implode` instead (#196) 
+
 # polars 0.6.0
 
 ## BREAKING CHANGES
diff --git a/R/expr__expr.R b/R/expr__expr.R
index 79b55e313..b86d69ced 100644
--- a/R/expr__expr.R
+++ b/R/expr__expr.R
@@ -1942,7 +1942,16 @@ Expr_product = "use_extendr_wrapper"
 #' pl$DataFrame(iris)$select(pl$col("Species")$n_unique())
 Expr_n_unique = "use_extendr_wrapper"
 
-
+#'  Approx count unique values
+#' @keywords Expr
+#' @description
+#' This is done using the HyperLogLog++ algorithm for cardinality estimation.
+#' @aliases approx_unique
+#' @return Expr
+#' @docType NULL
+#' @examples
+#' pl$DataFrame(iris)$select(pl$col("Species")$approx_unique())
+Expr_approx_unique = "use_extendr_wrapper"
 
 #' Count `Nulls`
 #' @keywords Expr
@@ -2232,9 +2241,8 @@ Expr_take_every = function(n) {
 #' @examples
 #' #get 3 first elements
 #' pl$DataFrame(list(x=1:11))$select(pl$col("x")$head(3))
-Expr_head = function(n=10) {
-  if(!is.numeric(n)) stopf("n must be numeric")
-  unwrap(.pr$Expr$head(self,n=n))
+Expr_head = function(n = 10) {
+  unwrap(.pr$Expr$head(self, n = n), "in $head():")
 }
 
 #' Tail
@@ -2248,9 +2256,8 @@ Expr_head = function(n=10) {
 #' @examples
 #' #get 3 last elements
 #' pl$DataFrame(list(x=1:11))$select(pl$col("x")$tail(3))
-Expr_tail = function(n=10) {
-  if(!is.numeric(n)) stopf("n must be numeric")
-  unwrap(.pr$Expr$tail(self,n=n))
+Expr_tail = function(n = 10) {
+  unwrap(.pr$Expr$tail(self, n = n), "in $tail():")
 }
 
 
@@ -3952,16 +3959,30 @@ Expr_set_sorted = function(reverse = FALSE) {
 
 
 #' Wrap column in list
-#' @description  Aggregate to list.
+#' @description  Aggregate values into a list.
 #' @keywords Expr
 #' @return Expr
 #' @aliases list
 #' @name Expr_list
-#' @details use to_struct to wrap a DataFrame
+#' @details use to_struct to wrap a DataFrame. Notice implode() is sometimes referred to
+#' as list() .
 #' @format a method
 #' @examples
-#' pl$select(pl$lit(1:4)$list(), pl$lit(c("a")))
-Expr_list = "use_extendr_wrapper"
+#' df = pl$DataFrame(
+#'   a = 1:3,
+#'   b = 4:6
+#' )
+#' df$select(pl$all()$implode())
+Expr_implode = "use_extendr_wrapper"
+
+##TODO REMOVE AT A BREAKING CHANGE
+Expr_list = function() {
+  if ( is.null(runtime_state$warned_deprecate_list)) {
+    runtime_state$warned_deprecate_list = TRUE
+    warning("polars pl$list and <Expr>$list are deprecated, use $implode instead.")
+  }
+  self$implode()
+}
 
 
 
diff --git a/R/extendr-wrappers.R b/R/extendr-wrappers.R
index 415f59ac3..6ec6182a7 100644
--- a/R/extendr-wrappers.R
+++ b/R/extendr-wrappers.R
@@ -427,7 +427,7 @@ Expr$entropy <- function(base, normalize) .Call(wrap__Expr__entropy, self, base,
 
 Expr$cumulative_eval <- function(expr, min_periods, parallel) .Call(wrap__Expr__cumulative_eval, self, expr, min_periods, parallel)
 
-Expr$list <- function() .Call(wrap__Expr__list, self)
+Expr$implode <- function() .Call(wrap__Expr__implode, self)
 
 Expr$shrink_dtype <- function() .Call(wrap__Expr__shrink_dtype, self)
 
@@ -641,6 +641,8 @@ Expr$map <- function(lambda, output_type, agg_list) .Call(wrap__Expr__map, self,
 
 Expr$is_unique <- function() .Call(wrap__Expr__is_unique, self)
 
+Expr$approx_unique <- function() .Call(wrap__Expr__approx_unique, self)
+
 Expr$is_first <- function() .Call(wrap__Expr__is_first, self)
 
 Expr$map_alias <- function(lambda) .Call(wrap__Expr__map_alias, self, lambda)
@@ -925,6 +927,8 @@ Series$rename_mut <- function(name) invisible(.Call(wrap__Series__rename_mut, se
 
 Series$dtype <- function() .Call(wrap__Series__dtype, self)
 
+Series$n_unique <- function() .Call(wrap__Series__n_unique, self)
+
 Series$name <- function() .Call(wrap__Series__name, self)
 
 Series$sort_mut <- function(reverse) .Call(wrap__Series__sort_mut, self, reverse)
diff --git a/R/functions.R b/R/functions__eager.R
similarity index 100%
rename from R/functions.R
rename to R/functions__eager.R
diff --git a/R/lazy_functions.R b/R/functions__lazy.R
similarity index 80%
rename from R/lazy_functions.R
rename to R/functions__lazy.R
index 495907336..086bfb218 100644
--- a/R/lazy_functions.R
+++ b/R/functions__lazy.R
@@ -71,7 +71,7 @@ pl$col = function(name="", ...) {
 
   #preconvert Series into char name(s)
   if(inherits(name,"Series")) name = name$to_vector()
-  
+
   name_add = list(...)
   if (length(name_add) > 0) {
     if (is_string(name) && all(sapply(name_add, is_string))) {
@@ -146,6 +146,27 @@ pl$count = function(column = NULL)  { # -> Expr | int:
   unwrap(result(pl$col(column)$count()), "in pl$count():")
 }
 
+#' Aggregate all column values into a list.
+#' @name pl_implode
+#' @param name Name of the column(s) that should be imploded, passed to pl$col()
+#' @keywords Expr
+#' @return Expr
+#' @examples
+#' pl$DataFrame(iris)$select(pl$implode("Species"))
+pl$implode = function(name) { # -> Expr
+  result(pl$col(name)) |>
+    map(.pr$Expr$implode) |>
+    unwrap("in pl$implode():")
+}
+
+##TODO REMOVE AT A BREAKING CHANGE
+pl$list = function(name) {
+  if ( is.null(runtime_state$warned_deprecate_list)) {
+    runtime_state$warned_deprecate_list = TRUE
+    warning("polars pl$list and <Expr>$list are deprecated, use $implode instead.")
+  }
+  pl$implode(name)
+}
 
 #' pl$first
 #' @name pl_first
@@ -232,6 +253,75 @@ pl$last = function(column = NULL) {#-> Expr | Any:
 }
 
 
+#' Get the first `n` rows.
+#' @name pl_head
+#' @param column if dtype is:
+#' - Series: Take head value in `Series`
+#' - str or int: syntactic sugar for `pl.col(..).head()`
+#' @param n Number of rows to take
+#' @keywords Expr_new
+#' @return Expr or head value of input Series
+#' @examples
+#' df = pl$DataFrame(
+#'   a = c(1, 8, 3),
+#'   b = c(4, 5, 2),
+#'   c = c("foo", "bar", "foo")
+#' )
+#'
+#' expr_head = pl$head("a")
+#' print(expr_head)
+#' df$select(expr_head)
+#'
+#' df$select(pl$head("a",2))
+#' pl$head(df$get_column("a"),2)
+pl$head = function(column, n = 10) {#-> Expr | Any:
+  pcase(
+    inherits(column,"Series"), result(column$expr$head(n)),
+    is.character(column), result(pl$col(column)$head(n)),
+    inherits(column,"Expr"), result(column$head(n)),
+    or_else = Err(paste0(
+      "param [column] type is neither Series, charvec nor Expr, but ",
+      str_string(column)
+    ))
+  ) |>
+    unwrap("in pl$head():")
+}
+
+
+#' Get the last `n` rows.
+#' @name pl_tail
+#' @param column if dtype is:
+#' - Series: Take tail value in `Series`
+#' - str or in: syntactic sugar for `pl.col(..).tail()`
+#' @param n Number of rows to take
+#' @return Expr or tail value of input Series
+#' @examples
+#' df = pl$DataFrame(
+#'   a = c(1, 8, 3),
+#'   b = c(4, 5, 2),
+#'   c = c("foo", "bar", "foo")
+#' )
+#'
+#' expr_tail = pl$head("a")
+#' print(expr_tail)
+#' df$select(expr_tail)
+#'
+#' df$select(pl$tail("a",2))
+#'
+#' pl$tail(df$get_column("a"),2)
+pl$tail = function(column, n = 10) {#-> Expr | Any:
+  pcase(
+    inherits(column,"Series"), result(column$expr$tail(n)),
+    is.character(column), result(pl$col(column)$tail(n)),
+    inherits(column,"Expr"), result(column$tail(n)),
+    or_else = Err(paste0(
+      "param [column] type is neither Series, charvec nor Expr, but ",
+      str_string(column)
+    ))
+  ) |>
+    unwrap("in pl$tail():")
+}
+
 #' pl$mean
 #' @name pl_mean
 #' @description Depending on the input type this function does different things:
@@ -321,10 +411,78 @@ pl$median = function(...) { #-> Expr | Any:
   unwrap("in pl$median():")
 }
 
+#' Count `n` unique values
+#' @name pl_n_unique
+#' @description Depending on the input type this function does different things:
+#' @param column if dtype is:
+#' - Series: call method n_unique() to return value of unique values.
+#' - String: syntactic sugar for `pl$col(column)$n_unique()`, returns Expr
+#' - Expr: syntactic sugar for `column$n_unique()`, returns Expr
+#'
+#' @keywords Expr_new
+#'
+#' @return Expr or value
+#'
+#' @examples
+#' #column as Series
+#' pl$n_unique(pl$Series(1:4)) == 4
+#'
+#' #column as String
+#' expr = pl$n_unique("bob")
+#' print(expr)
+#' pl$DataFrame(bob = 1:4)$select(expr)
+#'
+#' #colum as Expr
+#' pl$DataFrame(bob = 1:4)$select(pl$n_unique(pl$col("bob")))
+pl$n_unique = function(column) { #-> int or Expr
+  pcase(
+    inherits(column, c("Series","Expr")), result(column$n_unique()),
+    is_string(column), result(pl$col(column)$n_unique()),
+    or_else = Err(paste("arg [column] is neither Series, Expr or String, but", str_string(column)))
+  ) |>
+    unwrap("in pl$n_unique():")
+}
 
+#' Approximate count of unique values.
+#' @name pl_approx_unique
+#' @description This is done using the HyperLogLog++ algorithm for cardinality estimation.
+#' @param column if dtype is:
+#' - String: syntactic sugar for `pl$col(column)$approx_unique()`, returns Expr
+#' - Expr: syntactic sugar for `column$approx_unique()`, returns Expr
+#'
+#' @keywords Expr_new
+#'
+#' @return Expr
+#'
+#' @details The approx_unique is likely only warranted for large columns. See example.
+#' It appears approx_unique scales better than n_unique, such that the relative performance
+#' difference increases with column size.
+#'
+#' @examples
+#' #column as Series
+#' pl$approx_unique(pl$lit(1:4)) == 4
+#'
+#' #column as String
+#' expr = pl$approx_unique("bob")
+#' print(expr)
+#' pl$DataFrame(bob = 1:80)$select(expr)
+#'
+#' #colum as Expr
+#' pl$DataFrame(bob = 1:4)$select(pl$approx_unique(pl$col("bob")))
+#'
+#' # comparison with n_unique for 2 million integers. (try change example to 20 million ints)
+#' lit_series = pl$lit(c(1:1E6,1E6:1,1:1E6))
+#' system.time(pl$approx_unique(lit_series)$lit_to_s()$print())
+#' system.time(pl$n_unique(lit_series)$lit_to_s()$print())
+pl$approx_unique = function(column) { #-> int or Expr
+  pcase(
+    inherits(column, "Expr"), result(column$approx_unique()),
+    is_string(column), result(pl$col(column)$approx_unique()),
+    or_else = Err(paste("arg [column] is neither Expr or String, but", str_string(column)))
+  ) |>
+    unwrap("in pl$approx_unique():")
+}
 
-#TODO contribute polars, python pl.sum(list) states uses lambda, however it is folds expressions in rust
-#docs should reflect that
 
 #' sum across expressions / literals / Series
 #' @description  syntactic sugar for starting a expression with sum
diff --git a/R/whenthen.R b/R/functions__whenthen.R
similarity index 100%
rename from R/whenthen.R
rename to R/functions__whenthen.R
diff --git a/R/series__series.R b/R/series__series.R
index d4e2cff58..59a837902 100644
--- a/R/series__series.R
+++ b/R/series__series.R
@@ -333,12 +333,12 @@ Series_shape = method_as_property(function() {
 #' #make nested Series_list of Series_list of Series_Int32
 #' #using Expr syntax because currently more complete translated
 #' series_list = pl$DataFrame(list(a=c(1:5,NA_integer_)))$select(
-#'   pl$col("a")$list()$list()$append(
+#'   pl$col("a")$implode()$implode()$append(
 #'     (
-#'       pl$col("a")$head(2)$list()$append(
-#'         pl$col("a")$tail(1)$list()
+#'       pl$col("a")$head(2)$implode()$append(
+#'         pl$col("a")$tail(1)$implode()
 #'       )
-#'     )$list()
+#'     )$implode()
 #'   )
 #' )$get_column("a") # get series from DataFrame
 #'
@@ -1046,3 +1046,13 @@ Series_expr = method_as_property(function() {
 Series_to_lit = function() {
   pl$lit(self)
 }
+
+#' Count unique values in Series
+#' @description Return count of unique values in Series
+#' @keywords Series
+#' @return Expr
+#' @examples
+#' pl$Series(1:4)$n_unique()
+Series_n_unique = function() {
+  unwrap(.pr$Series$n_unique(self), "in $n_unique():")
+}
diff --git a/man/Expr_approx_unique.Rd b/man/Expr_approx_unique.Rd
new file mode 100644
index 000000000..7b6a24411
--- /dev/null
+++ b/man/Expr_approx_unique.Rd
@@ -0,0 +1,22 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/expr__expr.R
+\name{Expr_approx_unique}
+\alias{Expr_approx_unique}
+\alias{approx_unique}
+\title{Approx count unique values}
+\format{
+An object of class \code{character} of length 1.
+}
+\usage{
+Expr_approx_unique
+}
+\value{
+Expr
+}
+\description{
+This is done using the HyperLogLog++ algorithm for cardinality estimation.
+}
+\examples{
+pl$DataFrame(iris)$select(pl$col("Species")$approx_unique())
+}
+\keyword{Expr}
diff --git a/man/Expr_list.Rd b/man/Expr_list.Rd
index 1e95abc18..c85e1e9c4 100644
--- a/man/Expr_list.Rd
+++ b/man/Expr_list.Rd
@@ -3,24 +3,30 @@
 \docType{data}
 \name{Expr_list}
 \alias{Expr_list}
+\alias{Expr_implode}
 \alias{list}
 \title{Wrap column in list}
 \format{
 a method
 }
 \usage{
-Expr_list
+Expr_implode
 }
 \value{
 Expr
 }
 \description{
-Aggregate to list.
+Aggregate values into a list.
 }
 \details{
-use to_struct to wrap a DataFrame
+use to_struct to wrap a DataFrame. Notice implode() is sometimes referred to
+as list() .
 }
 \examples{
-pl$select(pl$lit(1:4)$list(), pl$lit(c("a")))
+df = pl$DataFrame(
+  a = 1:3,
+  b = 4:6
+)
+df$select(pl$all()$implode())
 }
 \keyword{Expr}
diff --git a/man/Expr_when_then_otherwise.Rd b/man/Expr_when_then_otherwise.Rd
index 68ddb148e..4248c7a0a 100644
--- a/man/Expr_when_then_otherwise.Rd
+++ b/man/Expr_when_then_otherwise.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/whenthen.R
+% Please edit documentation in R/functions__whenthen.R
 \name{Expr_when_then_otherwise}
 \alias{Expr_when_then_otherwise}
 \alias{when}
diff --git a/man/Series_n_unique.Rd b/man/Series_n_unique.Rd
new file mode 100644
index 000000000..edec6fd59
--- /dev/null
+++ b/man/Series_n_unique.Rd
@@ -0,0 +1,18 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/series__series.R
+\name{Series_n_unique}
+\alias{Series_n_unique}
+\title{Count unique values in Series}
+\usage{
+Series_n_unique()
+}
+\value{
+Expr
+}
+\description{
+Return count of unique values in Series
+}
+\examples{
+pl$Series(1:4)$n_unique()
+}
+\keyword{Series}
diff --git a/man/Series_to_r.Rd b/man/Series_to_r.Rd
index 72b2648ab..b0f71d5c6 100644
--- a/man/Series_to_r.Rd
+++ b/man/Series_to_r.Rd
@@ -44,12 +44,12 @@ series_vec$to_vector() #implicit call unlist(), same as to_r() as already vector
 #make nested Series_list of Series_list of Series_Int32
 #using Expr syntax because currently more complete translated
 series_list = pl$DataFrame(list(a=c(1:5,NA_integer_)))$select(
-  pl$col("a")$list()$list()$append(
+  pl$col("a")$implode()$implode()$append(
     (
-      pl$col("a")$head(2)$list()$append(
-        pl$col("a")$tail(1)$list()
+      pl$col("a")$head(2)$implode()$append(
+        pl$col("a")$tail(1)$implode()
       )
-    )$list()
+    )$implode()
   )
 )$get_column("a") # get series from DataFrame
 
diff --git a/man/dot-DollarNames.When.Rd b/man/dot-DollarNames.When.Rd
index 14ef4ddb0..9ffd048f0 100644
--- a/man/dot-DollarNames.When.Rd
+++ b/man/dot-DollarNames.When.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/whenthen.R
+% Please edit documentation in R/functions__whenthen.R
 \name{.DollarNames.When}
 \alias{.DollarNames.When}
 \title{auto complete $-access into a polars object}
diff --git a/man/dot-DollarNames.WhenThen.Rd b/man/dot-DollarNames.WhenThen.Rd
index 83c0a93e4..2c9111763 100644
--- a/man/dot-DollarNames.WhenThen.Rd
+++ b/man/dot-DollarNames.WhenThen.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/whenthen.R
+% Please edit documentation in R/functions__whenthen.R
 \name{.DollarNames.WhenThen}
 \alias{.DollarNames.WhenThen}
 \title{auto complete $-access into a polars object}
diff --git a/man/dot-DollarNames.WhenThenThen.Rd b/man/dot-DollarNames.WhenThenThen.Rd
index f9442ca31..ad772f87b 100644
--- a/man/dot-DollarNames.WhenThenThen.Rd
+++ b/man/dot-DollarNames.WhenThenThen.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/whenthen.R
+% Please edit documentation in R/functions__whenthen.R
 \name{.DollarNames.WhenThenThen}
 \alias{.DollarNames.WhenThenThen}
 \title{auto complete $-access into a polars object}
diff --git a/man/pl_all.Rd b/man/pl_all.Rd
index d2c11cfa2..3e6d4a451 100644
--- a/man/pl_all.Rd
+++ b/man/pl_all.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_all}
 \alias{pl_all}
 \title{New Expr referring to all columns}
diff --git a/man/pl_approx_unique.Rd b/man/pl_approx_unique.Rd
new file mode 100644
index 000000000..d2379f11f
--- /dev/null
+++ b/man/pl_approx_unique.Rd
@@ -0,0 +1,41 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/functions__lazy.R
+\name{pl_approx_unique}
+\alias{pl_approx_unique}
+\title{Approximate count of unique values.}
+\arguments{
+\item{column}{if dtype is:
+\itemize{
+\item String: syntactic sugar for \code{pl$col(column)$approx_unique()}, returns Expr
+\item Expr: syntactic sugar for \code{column$approx_unique()}, returns Expr
+}}
+}
+\value{
+Expr
+}
+\description{
+This is done using the HyperLogLog++ algorithm for cardinality estimation.
+}
+\details{
+The approx_unique is likely only warranted for large columns. See example.
+It appears approx_unique scales better than n_unique, such that the relative performance
+difference increases with column size.
+}
+\examples{
+#column as Series
+pl$approx_unique(pl$lit(1:4)) == 4
+
+#column as String
+expr = pl$approx_unique("bob")
+print(expr)
+pl$DataFrame(bob = 1:80)$select(expr)
+
+#colum as Expr
+pl$DataFrame(bob = 1:4)$select(pl$approx_unique(pl$col("bob")))
+
+# comparison with n_unique for 2 million integers. (try change example to 20 million ints)
+lit_series = pl$lit(c(1:1E6,1E6:1,1:1E6))
+system.time(pl$approx_unique(lit_series)$lit_to_s()$print())
+system.time(pl$n_unique(lit_series)$lit_to_s()$print())
+}
+\keyword{Expr_new}
diff --git a/man/pl_coalesce.Rd b/man/pl_coalesce.Rd
index ce7280a8d..15fddc306 100644
--- a/man/pl_coalesce.Rd
+++ b/man/pl_coalesce.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_coalesce}
 \alias{pl_coalesce}
 \title{Coalesce}
diff --git a/man/pl_col.Rd b/man/pl_col.Rd
index 395061ffb..8524e3da8 100644
--- a/man/pl_col.Rd
+++ b/man/pl_col.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_col}
 \alias{pl_col}
 \title{Start Expression with a column}
diff --git a/man/pl_concat.Rd b/man/pl_concat.Rd
index 966b04ebf..04fafab4a 100644
--- a/man/pl_concat.Rd
+++ b/man/pl_concat.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/functions.R
+% Please edit documentation in R/functions__eager.R
 \name{pl_concat}
 \alias{pl_concat}
 \title{Concat polars objects}
diff --git a/man/pl_concat_list.Rd b/man/pl_concat_list.Rd
index eb762b92e..4ae52de9d 100644
--- a/man/pl_concat_list.Rd
+++ b/man/pl_concat_list.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_concat_list}
 \alias{pl_concat_list}
 \title{Concat the arrays in a Series dtype List in linear time.}
diff --git a/man/pl_count.Rd b/man/pl_count.Rd
index 3101f188d..e50d48dc4 100644
--- a/man/pl_count.Rd
+++ b/man/pl_count.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_count}
 \alias{pl_count}
 \title{pl$count}
diff --git a/man/pl_date_range.Rd b/man/pl_date_range.Rd
index 5fd0f8bd1..48b60b732 100644
--- a/man/pl_date_range.Rd
+++ b/man/pl_date_range.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/functions.R
+% Please edit documentation in R/functions__eager.R
 \name{pl_date_range}
 \alias{pl_date_range}
 \title{new date_range}
diff --git a/man/pl_element.Rd b/man/pl_element.Rd
index c28904c6e..d28c89ec6 100644
--- a/man/pl_element.Rd
+++ b/man/pl_element.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_element}
 \alias{pl_element}
 \alias{element}
diff --git a/man/pl_first.Rd b/man/pl_first.Rd
index a217fe594..f608752fb 100644
--- a/man/pl_first.Rd
+++ b/man/pl_first.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_first}
 \alias{pl_first}
 \title{pl$first}
diff --git a/man/pl_head.Rd b/man/pl_head.Rd
new file mode 100644
index 000000000..727afd0e2
--- /dev/null
+++ b/man/pl_head.Rd
@@ -0,0 +1,35 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/functions__lazy.R
+\name{pl_head}
+\alias{pl_head}
+\title{Get the first \code{n} rows.}
+\arguments{
+\item{column}{if dtype is:
+\itemize{
+\item Series: Take head value in \code{Series}
+\item str or int: syntactic sugar for \verb{pl.col(..).head()}
+}}
+
+\item{n}{Number of rows to take}
+}
+\value{
+Expr or head value of input Series
+}
+\description{
+Get the first \code{n} rows.
+}
+\examples{
+df = pl$DataFrame(
+  a = c(1, 8, 3),
+  b = c(4, 5, 2),
+  c = c("foo", "bar", "foo")
+)
+
+expr_head = pl$head("a")
+print(expr_head)
+df$select(expr_head)
+
+df$select(pl$head("a",2))
+pl$head(df$get_column("a"),2)
+}
+\keyword{Expr_new}
diff --git a/man/pl_implode.Rd b/man/pl_implode.Rd
new file mode 100644
index 000000000..738f85cf7
--- /dev/null
+++ b/man/pl_implode.Rd
@@ -0,0 +1,18 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/functions__lazy.R
+\name{pl_implode}
+\alias{pl_implode}
+\title{Aggregate all column values into a list.}
+\arguments{
+\item{name}{Name of the column(s) that should be imploded, passed to pl$col()}
+}
+\value{
+Expr
+}
+\description{
+Aggregate all column values into a list.
+}
+\examples{
+pl$DataFrame(iris)$select(pl$implode("Species"))
+}
+\keyword{Expr}
diff --git a/man/pl_last.Rd b/man/pl_last.Rd
index 135ce00a7..027864e98 100644
--- a/man/pl_last.Rd
+++ b/man/pl_last.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_last}
 \alias{pl_last}
 \title{pl$last}
diff --git a/man/pl_max.Rd b/man/pl_max.Rd
index 9c653320d..dc837cfb8 100644
--- a/man/pl_max.Rd
+++ b/man/pl_max.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_max}
 \alias{pl_max}
 \title{max across expressions / literals / Series}
diff --git a/man/pl_mean.Rd b/man/pl_mean.Rd
index f296a2689..05efda657 100644
--- a/man/pl_mean.Rd
+++ b/man/pl_mean.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_mean}
 \alias{pl_mean}
 \title{pl$mean}
diff --git a/man/pl_median.Rd b/man/pl_median.Rd
index d9fa4d92d..7350971ff 100644
--- a/man/pl_median.Rd
+++ b/man/pl_median.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_median}
 \alias{pl_median}
 \title{pl$median}
diff --git a/man/pl_min.Rd b/man/pl_min.Rd
index 25f8704b8..572395107 100644
--- a/man/pl_min.Rd
+++ b/man/pl_min.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_min}
 \alias{pl_min}
 \title{min across expressions / literals / Series}
diff --git a/man/pl_n_unique.Rd b/man/pl_n_unique.Rd
new file mode 100644
index 000000000..3ba222785
--- /dev/null
+++ b/man/pl_n_unique.Rd
@@ -0,0 +1,32 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/functions__lazy.R
+\name{pl_n_unique}
+\alias{pl_n_unique}
+\title{Count \code{n} unique values}
+\arguments{
+\item{column}{if dtype is:
+\itemize{
+\item Series: call method n_unique() to return value of unique values.
+\item String: syntactic sugar for \code{pl$col(column)$n_unique()}, returns Expr
+\item Expr: syntactic sugar for \code{column$n_unique()}, returns Expr
+}}
+}
+\value{
+Expr or value
+}
+\description{
+Depending on the input type this function does different things:
+}
+\examples{
+#column as Series
+pl$n_unique(pl$Series(1:4)) == 4
+
+#column as String
+expr = pl$n_unique("bob")
+print(expr)
+pl$DataFrame(bob = 1:4)$select(expr)
+
+#colum as Expr
+pl$DataFrame(bob = 1:4)$select(pl$n_unique(pl$col("bob")))
+}
+\keyword{Expr_new}
diff --git a/man/pl_pl.Rd b/man/pl_pl.Rd
index 1ce8183f3..b476ff3a3 100644
--- a/man/pl_pl.Rd
+++ b/man/pl_pl.Rd
@@ -6,7 +6,7 @@
 \alias{pl}
 \title{The complete polars public API.}
 \format{
-An object of class \code{environment} of length 63.
+An object of class \code{environment} of length 69.
 }
 \usage{
 pl
diff --git a/man/pl_std.Rd b/man/pl_std.Rd
index a12992c05..b9832ccf4 100644
--- a/man/pl_std.Rd
+++ b/man/pl_std.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_std}
 \alias{pl_std}
 \title{Standard deviation}
diff --git a/man/pl_struct.Rd b/man/pl_struct.Rd
index 8761741ca..06c1b351d 100644
--- a/man/pl_struct.Rd
+++ b/man/pl_struct.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_struct}
 \alias{pl_struct}
 \alias{struct}
diff --git a/man/pl_sum.Rd b/man/pl_sum.Rd
index cf6ba93cf..c52860b69 100644
--- a/man/pl_sum.Rd
+++ b/man/pl_sum.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_sum}
 \alias{pl_sum}
 \title{sum across expressions / literals / Series}
diff --git a/man/pl_tail.Rd b/man/pl_tail.Rd
new file mode 100644
index 000000000..2c439785b
--- /dev/null
+++ b/man/pl_tail.Rd
@@ -0,0 +1,35 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/functions__lazy.R
+\name{pl_tail}
+\alias{pl_tail}
+\title{Get the last \code{n} rows.}
+\arguments{
+\item{column}{if dtype is:
+\itemize{
+\item Series: Take tail value in \code{Series}
+\item str or in: syntactic sugar for \verb{pl.col(..).tail()}
+}}
+
+\item{n}{Number of rows to take}
+}
+\value{
+Expr or tail value of input Series
+}
+\description{
+Get the last \code{n} rows.
+}
+\examples{
+df = pl$DataFrame(
+  a = c(1, 8, 3),
+  b = c(4, 5, 2),
+  c = c("foo", "bar", "foo")
+)
+
+expr_tail = pl$head("a")
+print(expr_tail)
+df$select(expr_tail)
+
+df$select(pl$tail("a",2))
+
+pl$tail(df$get_column("a"),2)
+}
diff --git a/man/pl_var.Rd b/man/pl_var.Rd
index 5747902a8..1431abf23 100644
--- a/man/pl_var.Rd
+++ b/man/pl_var.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/lazy_functions.R
+% Please edit documentation in R/functions__lazy.R
 \name{pl_var}
 \alias{pl_var}
 \title{Variance}
diff --git a/man/polars_options.Rd b/man/polars_options.Rd
index 98eafe28a..7633110b4 100644
--- a/man/polars_options.Rd
+++ b/man/polars_options.Rd
@@ -67,13 +67,13 @@ with \verb{pl$options$<name>(<value>)}
 setting an options may be rejected if not passing opt_requirements
 }
 \examples{
-#rename columns by naming expression, experimental requires option named_exprs = TRUE
+# rename columns by naming expression, experimental requires option named_exprs = TRUE
 pl$set_polars_options(named_exprs = TRUE)
 pl$DataFrame(iris)$with_columns(
-  pl$col("Sepal.Length")$abs(), #not named expr will keep name "Sepal.Length"
-  SW_add_2 = (pl$col("Sepal.Width")+2)
+  pl$col("Sepal.Length")$abs(), # not named expr will keep name "Sepal.Length"
+  SW_add_2 = (pl$col("Sepal.Width") + 2)
 )
- pl$get_polars_options()
+pl$get_polars_options()
 # polars options read via `pl$options$<name>()`
 pl$options$strictly_immutable()
 pl$options$default_maintain_order()
@@ -81,21 +81,23 @@ pl$options$default_maintain_order()
 # write via `pl$options$<name>(<value>)`, invalided values/types are rejected
 pl$options$default_maintain_order(TRUE)
 tryCatch(
-  {pl$options$default_maintain_order(42)},
+  {
+    pl$options$default_maintain_order(42)
+  },
   error = function(err) cat(as.character(err))
 )
 pl$set_polars_options(strictly_immutable = FALSE)
 pl$get_polars_options()
 
 
-#setting strictly_immutable = 42 will be rejected as
+# setting strictly_immutable = 42 will be rejected as
 tryCatch(
   pl$set_polars_options(strictly_immutable = 42),
-  error= function(e) print(e)
+  error = function(e) print(e)
 )
 
-#reset options like this
+# reset options like this
 pl$reset_polars_options()
-#use get_polars_opt_requirements() to requirements
+# use get_polars_opt_requirements() to requirements
 pl$get_polars_opt_requirements()
 }
diff --git a/man/print.When.Rd b/man/print.When.Rd
index a3a18e66c..88ac49989 100644
--- a/man/print.When.Rd
+++ b/man/print.When.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/whenthen.R
+% Please edit documentation in R/functions__whenthen.R
 \name{print.When}
 \alias{print.When}
 \title{print When}
diff --git a/man/print.WhenThen.Rd b/man/print.WhenThen.Rd
index b8e0cf8d4..7dea79184 100644
--- a/man/print.WhenThen.Rd
+++ b/man/print.WhenThen.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/whenthen.R
+% Please edit documentation in R/functions__whenthen.R
 \name{print.WhenThen}
 \alias{print.WhenThen}
 \title{print When}
diff --git a/man/print.WhenThenThen.Rd b/man/print.WhenThenThen.Rd
index 4438e6b2f..3ae1debb4 100644
--- a/man/print.WhenThenThen.Rd
+++ b/man/print.WhenThenThen.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/whenthen.R
+% Please edit documentation in R/functions__whenthen.R
 \name{print.WhenThenThen}
 \alias{print.WhenThenThen}
 \title{print When}
diff --git a/src/rust/Cargo.toml b/src/rust/Cargo.toml
index c17c8677a..66233efdf 100644
--- a/src/rust/Cargo.toml
+++ b/src/rust/Cargo.toml
@@ -117,7 +117,8 @@ features = [
   "is_unique",
   "binary_encoding",
   "string_from_radix",
-  "meta"
+  "meta",
+  "approx_unique",
   ]
 default-features = false
 git = "https://github.com/pola-rs/polars.git"
diff --git a/src/rust/src/lazy/dsl.rs b/src/rust/src/lazy/dsl.rs
index b074c9167..cf6ae450e 100644
--- a/src/rust/src/lazy/dsl.rs
+++ b/src/rust/src/lazy/dsl.rs
@@ -986,7 +986,7 @@ impl Expr {
         }))
     }
 
-    pub fn list(&self) -> Self {
+    pub fn implode(&self) -> Self {
         self.clone().0.implode().into()
     }
 
@@ -1541,18 +1541,12 @@ impl Expr {
         self.0.clone().last().into()
     }
 
-    pub fn head(&self, n: f64) -> List {
-        let res = try_f64_into_usize(n)
-            .map_err(|err| format!("in head: {}", err))
-            .map(|n| Expr(self.0.clone().head(Some(n))));
-        r_result_list(res)
+    pub fn head(&self, n: Robj) -> Result<Self, String> {
+        Ok(self.0.clone().head(Some(robj_to!(usize, n)?)).into())
     }
 
-    pub fn tail(&self, n: f64) -> List {
-        let res = try_f64_into_usize(n)
-            .map_err(|err| format!("in tail: {}", err))
-            .map(|n| Expr(self.0.clone().tail(Some(n))));
-        r_result_list(res)
+    pub fn tail(&self, n: Robj) -> Result<Self, String> {
+        Ok(self.0.clone().tail(Some(robj_to!(usize, n)?)).into())
     }
 
     //chaining methods
@@ -1684,6 +1678,10 @@ impl Expr {
         self.0.clone().is_unique().into()
     }
 
+    pub fn approx_unique(&self) -> Self {
+        self.clone().0.approx_unique().into()
+    }
+
     pub fn is_first(&self) -> Self {
         self.clone().0.is_first().into()
     }
diff --git a/src/rust/src/series.rs b/src/rust/src/series.rs
index bb322940b..896262767 100644
--- a/src/rust/src/series.rs
+++ b/src/rust/src/series.rs
@@ -93,6 +93,11 @@ impl Series {
         RPolarsDataType(self.0.dtype().clone())
     }
 
+    fn n_unique(&self) -> Result<usize, String> {
+        let n = self.0.n_unique().map_err(|err| err.to_string())?;
+        Ok(n)
+    }
+
     //wait inner_dtype until list supported
 
     pub fn name(&self) -> &str {
diff --git a/tests/testthat/test-dataframe.R b/tests/testthat/test-dataframe.R
index b1e30597c..074b41579 100644
--- a/tests/testthat/test-dataframe.R
+++ b/tests/testthat/test-dataframe.R
@@ -560,7 +560,10 @@ test_that("drop_nulls", {
   expect_equal(pl$DataFrame(tmp)$drop_nulls("mpg")$height, 29, ignore_attr = TRUE)
   expect_equal(pl$DataFrame(tmp)$drop_nulls("hp")$height, 32, ignore_attr = TRUE)
   expect_equal(pl$DataFrame(tmp)$drop_nulls(c("mpg", "hp"))$height, 29, ignore_attr = TRUE)
-  expect_error(pl$DataFrame(mtcars)$drop_nulls("bad")$height, pattern = "ColumnNotFound")
+  expect_grepl_error(
+    pl$DataFrame(mtcars)$drop_nulls("bad")$height,
+    "ColumnNotFound"
+  )
 })
 
 
diff --git a/tests/testthat/test-expr.R b/tests/testthat/test-expr.R
index 5ceaad339..531544921 100644
--- a/tests/testthat/test-expr.R
+++ b/tests/testthat/test-expr.R
@@ -903,7 +903,7 @@ test_that("Expr_k_top", {
   known = structure(list(k_top = c(Inf, 6, NaN), k_bot = c(NA, -Inf, 0)),
    row.names = c( NA, -3L), class = "data.frame")
   expect_equal(l_actual$to_data_frame(), known)
-  
+
   #TODO contribute polars k_top always places NaN first no matter reverse,
   # this behavour does not match Expr_sort
 })
@@ -1334,9 +1334,9 @@ test_that("arg_unique", {
 
   expect_identical(
     pl$DataFrame(l)$select(
-      pl$col("a")$arg_unique()$list(),
-      pl$col("b")$arg_unique()$list(),
-      pl$col("c")$arg_unique()$list()
+      pl$col("a")$arg_unique()$implode(),
+      pl$col("b")$arg_unique()$implode(),
+      pl$col("c")$arg_unique()$implode()
     )$to_list() |> lapply(\(x) x[[1]]) |>lapply(as.numeric)  ,
     list(
       a = which(!duplicated(l$a))-1.0,
@@ -1504,9 +1504,9 @@ test_that("is_between", {
 test_that("hash + reinterpret", {
   df = pl$DataFrame(iris)
 
-  hash_values1 = unname(unlist(df$select(pl$col(c("Sepal.Width","Species"))$unique()$hash()$list())$to_list()))
-  hash_values2 = unname(unlist(df$select(pl$col(c("Sepal.Width","Species"))$unique()$hash(1,2,3,4)$list())$to_list()))
-  hash_values3 = unname((df$select(pl$col(c("Sepal.Width","Species"))$unique()$hash(1,2,3,4)$list()$cast(pl$List(pl$Utf8)))$to_list()))
+  hash_values1 = unname(unlist(df$select(pl$col(c("Sepal.Width","Species"))$unique()$hash()$implode())$to_list()))
+  hash_values2 = unname(unlist(df$select(pl$col(c("Sepal.Width","Species"))$unique()$hash(1,2,3,4)$implode())$to_list()))
+  hash_values3 = unname((df$select(pl$col(c("Sepal.Width","Species"))$unique()$hash(1,2,3,4)$implode()$cast(pl$List(pl$Utf8)))$to_list()))
   expect_true(!any(duplicated(hash_values1)))
   expect_true(!any(sapply(hash_values3,\(x) any(duplicated(x)))))
 
@@ -1518,9 +1518,9 @@ test_that("hash + reinterpret", {
   # remove seed warning in docs
   expect_true(all(hash_values1==hash_values2)) #...however this is true
 
-  df_hash = df$select(pl$col(c("Sepal.Width","Species"))$unique()$hash(1,2,3,4)$list())
-  df_hash_same = df_hash$select(pl$all()$flatten()$reinterpret(FALSE)$list())
-  df_hash_rein = df_hash$select(pl$all()$flatten()$reinterpret(TRUE)$list())
+  df_hash = df$select(pl$col(c("Sepal.Width","Species"))$unique()$hash(1,2,3,4)$implode())
+  df_hash_same = df_hash$select(pl$all()$flatten()$reinterpret(FALSE)$implode())
+  df_hash_rein = df_hash$select(pl$all()$flatten()$reinterpret(TRUE)$implode())
 
 
   expect_identical(df_hash$to_list(),df_hash_same$to_list())
@@ -2009,8 +2009,8 @@ test_that("reshape", {
 
   expect_identical(
     pl$select(
-      pl$lit(1:12)$reshape(c(3,4))$alias("rs_3_4")$list(),
-      pl$lit(1:12)$reshape(c(4,3))$alias("rs_4_3")$list()
+      pl$lit(1:12)$reshape(c(3,4))$alias("rs_3_4")$implode(),
+      pl$lit(1:12)$reshape(c(4,3))$alias("rs_4_3")$implode()
     )$to_list(),
     list(
       rs_3_4 = list(r_reshape(1:12,c(4,3))),
@@ -2060,14 +2060,14 @@ test_that("shuffle", {
 test_that("sample", {
   df = pl$DataFrame(a=1:10)
   res = df$select(
-    pl$col("a")$sample(seed=1)$alias("default")$list(),
-    pl$col("a")$sample(n=3,seed=1)$alias("n3")$list(),
-    pl$col("a")$sample(frac=.4,seed=1)$alias("frac.4")$list(),
-    pl$col("a")$sample(frac=1,seed=1)$alias("frac2")$list(),
-    pl$col("a")$sample(frac=1,with_replacement=FALSE,seed=1)$alias("frac1norep")$list(),
-    pl$col("a")$sample(n = 10,with_replacement=FALSE,seed=1)$alias("n10norep")$list(),
-    pl$col("a")$sample(frac=1,with_replacement=FALSE,shuffle= TRUE,seed=1)$alias("frac1norepshuffle")$list(),
-    pl$col("a")$sample(n = 10,with_replacement=FALSE,shuffle= TRUE,seed=1)$alias("n10norep_shuffle")$list()
+    pl$col("a")$sample(seed=1)$alias("default")$implode(),
+    pl$col("a")$sample(n=3,seed=1)$alias("n3")$implode(),
+    pl$col("a")$sample(frac=.4,seed=1)$alias("frac.4")$implode(),
+    pl$col("a")$sample(frac=1,seed=1)$alias("frac2")$implode(),
+    pl$col("a")$sample(frac=1,with_replacement=FALSE,seed=1)$alias("frac1norep")$implode(),
+    pl$col("a")$sample(n = 10,with_replacement=FALSE,seed=1)$alias("n10norep")$implode(),
+    pl$col("a")$sample(frac=1,with_replacement=FALSE,shuffle= TRUE,seed=1)$alias("frac1norepshuffle")$implode(),
+    pl$col("a")$sample(n = 10,with_replacement=FALSE,shuffle= TRUE,seed=1)$alias("n10norep_shuffle")$implode()
   )$to_list() |> lapply(unlist)
 
   expect_identical(
@@ -2356,3 +2356,12 @@ test_that("concat_list", {
   )
 
 })
+
+
+test_that("implode", {
+  expect_identical(pl$lit(1:4)$implode()$explode()$to_r(),1:4)
+  expect_identical(pl$lit(1:4)$implode()$to_r(),list(1:4))
+  expect_identical(pl$lit(1:4)$implode()$to_r(),pl$lit(list(1:4))$to_r())
+  expect_grepl_error(pl$lit(42)$implode(42),c("unused argument"))
+})
+
diff --git a/tests/testthat/test-lazy.R b/tests/testthat/test-lazy.R
index 46c952b0a..19058fb09 100644
--- a/tests/testthat/test-lazy.R
+++ b/tests/testthat/test-lazy.R
@@ -215,7 +215,10 @@ test_that("drop_nulls", {
   expect_equal(pl$DataFrame(tmp)$lazy()$drop_nulls("mpg")$collect()$height, 29, ignore_attr = TRUE)
   expect_equal(pl$DataFrame(tmp)$lazy()$drop_nulls("hp")$collect()$height, 32, ignore_attr = TRUE)
   expect_equal(pl$DataFrame(tmp)$lazy()$drop_nulls(c("mpg", "hp"))$collect()$height, 29, ignore_attr = TRUE)
-  expect_error(pl$DataFrame(mtcars)$lazy()$drop_nulls("bad")$collect()$height, pattern = "ColumnNotFound")
+  expect_grepl_error(
+    pl$DataFrame(mtcars)$lazy()$drop_nulls("bad")$collect()$height,
+    "ColumnNotFound"
+  )
 })
 
 test_that("fill_nulls", {
diff --git a/tests/testthat/test-lazy_functions.R b/tests/testthat/test-lazy_functions.R
index 1613be6c4..a07248193 100644
--- a/tests/testthat/test-lazy_functions.R
+++ b/tests/testthat/test-lazy_functions.R
@@ -177,5 +177,110 @@ test_that("pl$count", {
 
 
 
+test_that("pl$implode", {
+  act = pl$implode("bob")
+  exp = pl$col("bob")$implode()
+  expect_true(act$meta$eq(exp))
+  expect_grepl_error(pl$implode(42),c("in pl\\$implode()","not supported"))
+})
+
+
+test_that("pl$n_unique", {
+
+  x = c(1:4, NA, NaN, 1) #6 unique one repeated
+  expect_identical(pl$n_unique(pl$Series(x)),6)
+
+  expr_act = pl$n_unique("bob")
+  expect_true(expr_act$meta$eq(pl$col("bob")$n_unique()))
+
+  expr_act_2 = pl$n_unique(pl$all())
+  expect_true(expr_act_2$meta$eq(pl$all()$n_unique()))
+
+  expect_grepl_error(pl$n_unique(1:99),c("in pl\\$n_unique","is neither","1 2 3"))
+})
+
+test_that("pl$approx_unique", {
+
+  x = c(1:4, NA, NaN, 1) #6 unique one repeated
+  expect_identical(pl$approx_unique(pl$lit(x))$to_r(),6)
+  expect_identical(pl$lit(x)$approx_unique()$to_r(),6)
+
+  #string input becomes a column
+  expect_true( pl$approx_unique("bob")$meta$pop()[[1]]$meta$eq(pl$col("bob")))
+
+  expr_act = pl$approx_unique("bob")
+  expect_true(expr_act$meta$eq(pl$col("bob")$approx_unique()))
+
+  expr_act_2 = pl$approx_unique(pl$all())
+  expect_true(expr_act_2$meta$eq(pl$all()$approx_unique()))
+
+  expect_grepl_error(pl$approx_unique(1:99),c("in pl\\$approx_unique","is neither","1 2 3"))
+})
+
+
+test_that("pl$head", {
+  df = pl$DataFrame(
+    a = c(1, 8, 3),
+    b = c(4, 5, 2),
+    c = c("foo", "bar", "foo")
+  )
+  expect_identical(
+    df$select(pl$head("a"))$to_data_frame()$a,
+    head(df$to_data_frame())$a
+  )
 
+  expect_identical(
+    df$select(pl$head("a",2))$to_data_frame()$a,
+    head(df$to_data_frame(),2)$a
+  )
 
+  expect_identical(
+    df$select(pl$head(pl$col("a"),2))$to_data_frame()$a,
+    head(df$to_data_frame(),2)$a
+  )
+
+  expect_identical(
+    pl$head(df$get_column("a"),2)$to_r(),
+    head(df$to_list()$a,2)
+  )
+
+  expect_grepl_error(
+    pl$head(df$get_column("a"),-2),
+    "the arg \\[n\\] the value -2 cannot be less than zero"
+  )
+
+})
+
+
+test_that("pl$tail", {
+  df = pl$DataFrame(
+    a = c(1, 8, 3),
+    b = c(4, 5, 2),
+    c = c("foo", "bar", "foo")
+  )
+  expect_identical(
+    df$select(pl$tail("a"))$to_data_frame()$a,
+    tail(df$to_data_frame())$a
+  )
+
+  expect_identical(
+    df$select(pl$tail("a",2))$to_data_frame()$a,
+    tail(df$to_data_frame(),2)$a
+  )
+
+  expect_identical(
+    df$select(pl$tail(pl$col("a"),2))$to_data_frame()$a,
+    tail(df$to_data_frame(),2)$a
+  )
+
+  expect_identical(
+    pl$tail(df$get_column("a"),2)$to_r(),
+    tail(df$to_list()$a,2)
+  )
+
+  expect_grepl_error(
+    pl$tail(df$get_column("a"),-2),
+    "the arg \\[n\\] the value -2 cannot be less than zero"
+  )
+
+})
diff --git a/tests/testthat/test-series.R b/tests/testthat/test-series.R
index f56fe3834..03650112e 100644
--- a/tests/testthat/test-series.R
+++ b/tests/testthat/test-series.R
@@ -422,12 +422,12 @@ test_that("rep", {
 
 test_that("Series list", {
   series_list <- pl$DataFrame(list(a = c(1:5, NA_integer_)))$select(
-    pl$col("a")$list()$list()$append(
+    pl$col("a")$implode()$implode()$append(
       (
-        pl$col("a")$head(2)$list()$append(
-          pl$col("a")$tail(1)$list()
+        pl$col("a")$head(2)$implode()$append(
+          pl$col("a")$tail(1)$implode()
         )
-      )$list()
+      )$implode()
     )
   )$get_column("a") # get series from DataFrame
 
@@ -525,3 +525,10 @@ patrick::with_parameters_test_that("mean, median, std, var", {
   },
   .cases = make_cases()
 )
+
+
+test_that("n_unique", {
+  x = c(1:4, NA, NaN, 1) #6 unique one repeated
+  expect_identical(pl$Series(x)$n_unique(),6)
+  expect_grepl_error(pl$Series(c())$n_unique(),"operation not supported for dtype")
+})
diff --git a/vignettes/userguide.Rmd b/vignettes/userguide.Rmd
index b4215a887..547ca861f 100755
--- a/vignettes/userguide.Rmd
+++ b/vignettes/userguide.Rmd
@@ -194,7 +194,7 @@ df$select(
 df$select(
   pl$col("*"),  # select all
   pl$col("random")$sum()$over("groups")$alias("sumc(random)/groups"),
-  pl$col("random")$list()$over("names")$alias("random/name")
+  pl$col("random")$implode()$over("names")$alias("random/name")
 )
 ```
 
@@ -423,23 +423,23 @@ pl$sum("foo")$over("groups")
 (pl$col("x")$sum() * pl$col("y"))$over("groups")
 
 # sum within a group and multiply with group elements 
-# and aggregate the group to a list
+# and aggregate/implode the group to a list
 # output type: -> List(Int32)
-(pl$col("x")$sum() * pl$col("y"))$list()$over("groups")
+(pl$col("x")$sum() * pl$col("y"))$implode()$over("groups")
 
-# note that it will require an explicit `list()` call
+# note that it will require an explicit `implode()` call
 # sum within a group and multiply with group elements 
-# and aggregate the group to a list
-# the flatten call explodes that list
+# and aggregate/implode the group to a list
+# the explode call unpack the list and combine inner elements to one column
 
 # This is the fastest method to do things over groups when the groups are sorted
-(pl$col("x")$sum() * pl$col("y"))$list()$over("groups")$flatten()
+(pl$col("x")$sum() * pl$col("y"))$implode()$over("groups")$explode()
 
 df$sort("Type 1")$select(
-  pl$col("Type 1")$head(3)$list()$over("Type 1")$flatten(),
-  pl$col("Name")$sort_by(pl$col("Speed"))$head(3)$list()$over("Type 1")$flatten()$alias("fastest/group"),
-  pl$col("Name")$sort_by(pl$col("Attack"))$head(3)$list()$over("Type 1")$flatten()$alias("strongest/group"),
-  pl$col("Name")$sort()$head(3)$list()$over("Type 1")$flatten()$alias("sorted_by_alphabet")
+  pl$col("Type 1")$head(3)$implode()$over("Type 1")$explode(),
+  pl$col("Name")$sort_by(pl$col("Speed"))$head(3)$implode()$over("Type 1")$explode()$alias("fastest/group"),
+  pl$col("Name")$sort_by(pl$col("Attack"))$head(3)$implode()$over("Type 1")$explode()$alias("strongest/group"),
+  pl$col("Name")$sort()$head(3)$implode()$over("Type 1")$explode()$alias("sorted_by_alphabet")
 )
 ```