float:truncate

5 files changed, 43 insertions, 4 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 417e7e1..b43e9b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,8 +9,8 @@
 - `str` module gains `append` function and loses `from_int`, `parse_int`,
   `from_float`, `parse_float`, and `base_from_int`.
 - `int` module created with `parse`, `to_string`, and `to_base_string`.
-- `float` module created with `ceiling`, `floor`, `round`, `parse`, and
-  `to_string`.
+- `float` module created with `ceiling`, `floor`, `round`, `truncate`,
+  `parse`, and `to_string`.
 
 ## v0.1.1 - 2019-04-17
 
diff --git a/gen/src/float.erl b/gen/src/float.erl
index f9e4064..cd1385c 100644
--- a/gen/src/float.erl
+++ b/gen/src/float.erl
@@ -1,7 +1,7 @@
 -module(float).
 -compile(no_auto_import).
 
--export([parse/1, to_string/1, ceiling/1, floor/1, round/1]).
+-export([parse/1, to_string/1, ceiling/1, floor/1, round/1, truncate/1]).
 
 parse(A) ->
     gleam__stdlib:parse_float(A).
@@ -17,3 +17,6 @@ floor(A) ->
 
 round(A) ->
     erlang:round(A).
+
+truncate(A) ->
+    erlang:trunc(A).
diff --git a/gen/test/float_test.erl b/gen/test/float_test.erl
index ecd210b..36eb3ad 100644
--- a/gen/test/float_test.erl
+++ b/gen/test/float_test.erl
@@ -1,7 +1,7 @@
 -module(float_test).
 -compile(no_auto_import).
 
--export([parse_test/0, to_string_test/0, ceiling_test/0, floor_test/0, round_test/0]).
+-export([parse_test/0, to_string_test/0, ceiling_test/0, floor_test/0, round_test/0, truncate_test/0]).
 
 parse_test() ->
     expect:equal(float:parse(<<"1.23">>), {ok, 1.23}),
@@ -32,3 +32,11 @@ round_test() ->
     expect:equal(float:round(8.5), 9),
     expect:equal(float:round(-8.1), -8),
     expect:equal(float:round(-7.5), -8).
+
+truncate_test() ->
+    expect:equal(float:truncate(8.1), 8),
+    expect:equal(float:truncate(8.4), 8),
+    expect:equal(float:truncate(8.499), 8),
+    expect:equal(float:truncate(8.5), 8),
+    expect:equal(float:truncate(-8.1), -8),
+    expect:equal(float:truncate(-7.5), -7).
diff --git a/src/float.gleam b/src/float.gleam
index 8902a82..5840606 100644
--- a/src/float.gleam
+++ b/src/float.gleam
@@ -17,3 +17,5 @@ pub external fn ceiling(Float) -> Float = "math" "ceil";
 pub external fn floor(Float) -> Float = "math" "floor";
 
 pub external fn round(Float) -> Int = "erlang" "round";
+
+pub external fn truncate(Float) -> Int = "erlang" "trunc";
diff --git a/test/float_test.gleam b/test/float_test.gleam
index a3bf4c1..db879b8 100644
--- a/test/float_test.gleam
+++ b/test/float_test.gleam
@@ -90,3 +90,29 @@ pub fn round_test() {
   |> float:round
   |> expect:equal(_, -8)
 }
+
+pub fn truncate_test() {
+  8.1
+  |> float:truncate
+  |> expect:equal(_, 8)
+
+  8.4
+  |> float:truncate
+  |> expect:equal(_, 8)
+
+  8.499
+  |> float:truncate
+  |> expect:equal(_, 8)
+
+  8.5
+  |> float:truncate
+  |> expect:equal(_, 8)
+
+  -8.1
+  |> float:truncate
+  |> expect:equal(_, -8)
+
+  -7.5
+  |> float:truncate
+  |> expect:equal(_, -7)
+}