Add method ifElse

README.md

@@ -291,7 +291,7 @@ R.hasPath(['b'], child) # True
 - [x] 0.1.2 head
 - [ ] identical
 - [x] 0.1.2 identity
-- [ ] ifElse
+- [x] ifElse
 - [ ] inc
 - [ ] includes
 - [ ] indexBy

ramda/__init__.py

@@ -47,6 +47,7 @@
 from .hasPath import hasPath
 from .head import head
 from .identity import identity
+from .ifElse import ifElse
 from .indexOf import indexOf
 from .insert import insert
 from .intersection import intersection

ramda/ifElse.py

@@ -0,0 +1,14 @@
+from .curryN import curryN
+from .private._curry3 import _curry3
+from .private._inspect import funcArgsLength
+
+
+def inner_ifElse(condition, onTrue, onFalse):
+  def _ifElse(*args):
+    if condition(*args):
+      return onTrue(*args)
+    return onFalse(*args)
+  return curryN(max(funcArgsLength(condition), funcArgsLength(onTrue), funcArgsLength(onFalse)), _ifElse)
+
+
+ifElse = _curry3(inner_ifElse)

test/test_ifElse.py

@@ -0,0 +1,76 @@
+
+import unittest
+
+import ramda as R
+from ramda.private._inspect import funcArgsLength
+
+"""
+https://github.com/ramda/ramda/blob/master/test/ifElse.js
+"""
+
+
+def t(a): return a + 1
+def v(a): return isinstance(a, int)
+
+
+identity = R.identity
+def isArray(xs): return isinstance(xs, list)
+
+
+class TestIfElse(unittest.TestCase):
+  def test_calls_the_truth_case_function_if_the_validator_returns_a_truthy_value(self):
+    self.assertEqual(11, R.ifElse(v, t, identity)(10))
+
+  def test_calls_the_false_case_function_if_the_validator_returns_a_falsy_value(self):
+    def v(a): return isinstance(a, int)
+    self.assertEqual('hello', R.ifElse(v, t, identity)('hello'))
+
+  def test_calls_the_true_case_on_array_items_and_the_false_case_on_non_array_items(self):
+    arr = [[1, 2, 3, 4, 5], 10, [0, 1], 15]
+    arrayToLength = R.map(R.ifElse(isArray, R.length, identity))
+    self.assertEqual([5, 10, 2, 15], arrayToLength(arr))
+
+  def test_passes_the_arguments_to_the_true_case_function(self):
+    def v(*_): return True
+
+    def onTrue(a, b):
+      self.assertEqual(a, 123)
+      self.assertEqual(b, 'abc')
+
+    R.ifElse(v, onTrue, identity)(123, 'abc')
+
+  def test_passes_the_arguments_to_the_false_case_function(self):
+    def v(*_): return False
+
+    def onFalse(a, b):
+      self.assertEqual(a, 123)
+      self.assertEqual(b, 'abc')
+
+    R.ifElse(v, identity, onFalse)(123, 'abc')
+
+  def test_returns_a_function_whose_arity_equals_the_max_arity_of_the_three_arguments_to_ifElse(self):
+    def a0(): return 0
+    def a1(x): return x
+    def a2(x, y): return x + y
+
+    self.assertEqual(2, funcArgsLength(R.ifElse(a0, a1, a2)))
+    self.assertEqual(2, funcArgsLength(R.ifElse(a0, a2, a1)))
+    self.assertEqual(2, funcArgsLength(R.ifElse(a1, a0, a2)))
+    self.assertEqual(2, funcArgsLength(R.ifElse(a1, a2, a0)))
+    self.assertEqual(2, funcArgsLength(R.ifElse(a2, a0, a1)))
+    self.assertEqual(2, funcArgsLength(R.ifElse(a2, a1, a0)))
+
+  def test_returns_a_curried_function(self):
+    ifIsNumber = R.ifElse(v)
+    self.assertEqual(16, ifIsNumber(t, identity)(15))
+    self.assertEqual('hello', ifIsNumber(t, identity)('hello'))
+
+    fn = R.ifElse(R.gt, R.subtract, R.add)
+    self.assertEqual(9, fn(2)(7))
+    self.assertEqual(9, fn(2, 7))
+    self.assertEqual(5, fn(7)(2))
+    self.assertEqual(5, fn(7, 2))
+
+
+if __name__ == '__main__':
+  unittest.main()