From a1e18a186d21f90a4e9c67ea2cf7e37d2d49edb3 Mon Sep 17 00:00:00 2001
From: Mike Lin <mlin@mlin.net>
Date: Fri, 28 Jun 2019 15:10:05 -0700
Subject: [PATCH] transpose()

---
 WDL/StdLib.py         | 18 ++++++++++++++++--
 tests/test_5stdlib.py | 22 ++++++++++++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/WDL/StdLib.py b/WDL/StdLib.py
index f187b09d..678bc864 100644
--- a/WDL/StdLib.py
+++ b/WDL/StdLib.py
@@ -616,8 +616,22 @@ def infer_type(self, expr: E.Apply) -> T.Base:
         return expr.arguments[0].type
 
     def _call_eager(self, expr: E.Apply, arguments: List[V.Base]) -> V.Base:
-        raise NotImplementedError()
-
+        ty = self.infer_type(expr)
+        assert isinstance(ty, T.Array) and isinstance(ty.item_type, T.Array)
+        mat = arguments[0].coerce(ty)
+        assert isinstance(mat, V.Array)
+        n = None
+        ans = []
+        for row in mat.value:
+            assert isinstance(row, V.Array)
+            if n is None:
+                n = len(row.value)
+                ans = [V.Array(ty.item_type, []) for _ in row.value]
+            if len(row.value) != n:
+                raise Error.EvalError(expr, "transpose(): ragged input matrix")
+            for i in range(len(row.value)):
+                ans[i].value.append(row.value[i])
+        return V.Array(ty, ans)
 
 class _Range(EagerFunction):
     # int -> int array
diff --git a/tests/test_5stdlib.py b/tests/test_5stdlib.py
index 75ccc19b..31ce8e70 100644
--- a/tests/test_5stdlib.py
+++ b/tests/test_5stdlib.py
@@ -464,3 +464,25 @@ def test_write(self):
         with open(outputs["o_json"]) as infile:
             self.assertEqual(json.load(infile), {"key1": "value1", "key2": "value2"})
         self.assertEqual(outputs["o_tsv"], [["one", "two", "three"], ["un", "deux", "trois"]])
+
+    def test_transpose(self):
+        outputs = self._test_task(R"""
+        version 1.0
+        task hello {
+            command {}
+            output {
+                Array[Array[Int]] mat = transpose([[0, 1, 2], [3, 4, 5]])
+            }
+        }
+        """)
+        self.assertEqual(outputs["mat"], [[0, 3], [1, 4], [2, 5]])
+
+        outputs = self._test_task(R"""
+        version 1.0
+        task hello {
+            command {}
+            output {
+                Array[Array[Int]] mat = transpose([[0, 1, 2], [3, 4, 5], []])
+            }
+        }
+        """, expected_exception=WDL.Error.EvalError)