From e5e14239bd6ca6f349b7dd76fb845b60515e3364 Mon Sep 17 00:00:00 2001
From: Erik Terpstra <39518+eterps@users.noreply.github.com>
Date: Tue, 19 May 2020 10:19:27 +0200
Subject: string.pad_left & string.pad_right

---
 src/gleam/string.gleam | 68 +++++++++++++++++++++++++++-----------------------
 src/gleam_stdlib.erl   |  5 +++-
 2 files changed, 41 insertions(+), 32 deletions(-)

(limited to 'src')

diff --git a/src/gleam/string.gleam b/src/gleam/string.gleam
index dd292b5..d5523ef 100644
--- a/src/gleam/string.gleam
+++ b/src/gleam/string.gleam
@@ -298,37 +298,6 @@ pub fn join(strings: List(String), with separator: String) -> String {
   |> iodata.from_strings
   |> iodata.to_string
 }
-///
-// TODO
-// Pad a string on the left until it has at least given number of Graphemes.
-//
-// ## Examples
-//    > pad_left("121", to: 5, with: ".")
-//    "..121"
-//
-//    > pad_left("121", to: 3, with: ".")
-//    "121"
-//
-//    > pad_left("121", to: 2, with: ".")
-//    "121"
-//
-//
-// pub fn pad_left(string: String, to size: Int, with: String) {}
-// TODO
-// Pad a string on the right until it has a given length.
-//
-// ## Examples
-//    > pad_right("121", to: 5, with: ".")
-//    "121.."
-//
-//    > pad_right("121", to: 3, with: ".")
-//    "121"
-//
-//    > pad_right("121", to: 2, with: ".")
-//    "121"
-//
-//
-// pub fn pad_right(string: String, to size: Int, with: String) {}
 
 type Direction {
   Leading
@@ -336,6 +305,43 @@ type Direction {
   Both
 }
 
+external fn erl_pad(String, Int, Direction, String) -> String =
+  "gleam_stdlib" "string_pad"
+
+/// Pad a string on the left until it has at least given number of Graphemes.
+///
+/// ## Examples
+///    > pad_left("121", to: 5, with: ".")
+///    "..121"
+///
+///    > pad_left("121", to: 3, with: ".")
+///    "121"
+///
+///    > pad_left("121", to: 2, with: ".")
+///    "121"
+///
+///
+pub fn pad_left(string: String, to length: Int, with pad_string: String) {
+  erl_pad(string, length, Leading, pad_string)
+}
+
+/// Pad a string on the right until it has a given length.
+///
+/// ## Examples
+///    > pad_right("121", to: 5, with: ".")
+///    "121.."
+///
+///    > pad_right("121", to: 3, with: ".")
+///    "121"
+///
+///    > pad_right("121", to: 2, with: ".")
+///    "121"
+///
+///
+pub fn pad_right(string: String, to length: Int, with pad_string: String) {
+  erl_pad(string, length, Trailing, pad_string)
+}
+
 external fn erl_trim(String, Direction) -> String =
   "string" "trim"
 
diff --git a/src/gleam_stdlib.erl b/src/gleam_stdlib.erl
index fbd84da..bbf7630 100644
--- a/src/gleam_stdlib.erl
+++ b/src/gleam_stdlib.erl
@@ -7,7 +7,7 @@
          iodata_append/2, iodata_prepend/2, identity/1, decode_int/1,
          decode_string/1, decode_bool/1, decode_float/1, decode_thunk/1, decode_atom/1,
          decode_list/1, decode_field/2, decode_element/2, parse_int/1, parse_float/1, compare_strings/2,
-         string_contains/2, string_starts_with/2, string_ends_with/2]).
+         string_contains/2, string_starts_with/2, string_ends_with/2, string_pad/4]).
 
 should_equal(Actual, Expected) -> ?assertEqual(Expected, Actual).
 should_not_equal(Actual, Expected) -> ?assertNotEqual(Expected, Actual).
@@ -139,3 +139,6 @@ string_ends_with(String, Suffix) when byte_size(Suffix) > byte_size(String) -> f
 string_ends_with(String, Suffix) ->
     SuffixSize = byte_size(Suffix),
     Suffix == binary_part(String, byte_size(String) - SuffixSize, SuffixSize).
+
+string_pad(String, Length, Dir, PadString) ->
+    unicode:characters_to_binary(string:pad(String, Length, Dir, PadString)).
-- 
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