py: implement map

go-python · sbinet · Jun 8, 2023 · Jun 7, 2023 · Jun 7, 2023 · Jun 7, 2023
commit 487fbd9f5878147c7cd5edb10718709dfde014ae
diff --git a/py/map.go b/py/map.go
@@ -0,0 +1,60 @@
+// Copyright 2023 The go-python Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package py
+
+// A python Map object
+type Map struct {
+	iters Tuple
+	fun   Object
+}
+
+var MapType = NewTypeX("filter", `map(func, *iterables) --> map object
+
+Make an iterator that computes the function using arguments from
+each of the iterables.  Stops when the shortest iterable is exhausted.`,
+	MapTypeNew, nil)
+
+// Type of this object
+func (m *Map) Type() *Type {
+	return FilterType
+}
+
+// MapType
+func MapTypeNew(metatype *Type, args Tuple, kwargs StringDict) (res Object, err error) {
+	numargs := len(args)
+	if numargs < 2 {
+		return nil, ExceptionNewf(TypeError, "map() must have at least two arguments.")
+	}
+	iters := make(Tuple, numargs-1)
+	for i := 1; i < numargs; i++ {
+		iters[i-1], err = Iter(args[i])
+		if err != nil {
+			return nil, err
+		}
+	}
+	return &Map{iters: iters, fun: args[0]}, nil
+}
+
+func (m *Map) M__iter__() (Object, error) {
+	return m, nil
+}
+
+func (m *Map) M__next__() (Object, error) {
+	numargs := len(m.iters)
+	argtuple := make(Tuple, numargs)
+
+	for i := 0; i < numargs; i++ {
+		val, err := Next(m.iters[i])
+		if err != nil {
+			return nil, err
+		}
+		argtuple[i] = val
+	}
+	return Call(m.fun, argtuple, nil)
+}
+
+// Check interface is satisfied
+var _ I__iter__ = (*Map)(nil)
+var _ I__next__ = (*Map)(nil)
diff --git a/py/tests/map.py b/py/tests/map.py
@@ -0,0 +1,54 @@
+# test_builtin.py:BuiltinTest.test_map()
+from libtest import assertRaises
+
+doc="map"
+class Squares:
+    def __init__(self, max):
+        self.max = max
+        self.sofar = []
+
+    def __len__(self): return len(self.sofar)
+
+    def __getitem__(self, i):
+        if not 0 <= i < self.max: raise IndexError
+        n = len(self.sofar)
+        while n <= i:
+            self.sofar.append(n*n)
+            n += 1
+        return self.sofar[i]
+
+assert list(map(lambda x: x*x, range(1,4))) == [1, 4, 9]
+try:
+    from math import sqrt
+except ImportError:
+    def sqrt(x):
+        return pow(x, 0.5)
+assert list(map(lambda x: list(map(sqrt, x)), [[16, 4], [81, 9]])) == [[4.0, 2.0], [9.0, 3.0]]
+assert list(map(lambda x, y: x+y, [1,3,2], [9,1,4])) == [10, 4, 6]
+
+def plus(*v):
+    accu = 0
+    for i in v: accu = accu + i
+    return accu
+assert list(map(plus, [1, 3, 7])) == [1, 3, 7]
+assert list(map(plus, [1, 3, 7], [4, 9, 2])) == [1+4, 3+9, 7+2]
+assert list(map(plus, [1, 3, 7], [4, 9, 2], [1, 1, 0])) == [1+4+1, 3+9+1, 7+2+0]
+assert list(map(int, Squares(10))) == [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
+def Max(a, b):
+    if a is None:
+        return b
+    if b is None:
+        return a
+    return max(a, b)
+assert list(map(Max, Squares(3), Squares(2))) == [0, 1]
+assertRaises(TypeError, map)
+assertRaises(TypeError, map, lambda x: x, 42)
+class BadSeq:
+    def __iter__(self):
+        raise ValueError
+        yield None
+assertRaises(ValueError, list, map(lambda x: x, BadSeq()))
+def badfunc(x):
+    raise RuntimeError
+assertRaises(RuntimeError, list, map(badfunc, range(5)))
+doc="finished"
diff --git a/stdlib/builtin/builtin.go b/stdlib/builtin/builtin.go
@@ -81,9 +81,9 @@ func init() {
 		"float":       py.FloatType,
 		"frozenset":   py.FrozenSetType,
 		// "property":       py.PropertyType,
-		"int":  py.IntType, // FIXME LongType?
-		"list": py.ListType,
-		// "map":            py.MapType,
+		"int":    py.IntType, // FIXME LongType?
+		"list":   py.ListType,
+		"map":    py.MapType,
 		"object": py.ObjectType,
 		"range":  py.RangeType,
 		// "reversed":       py.ReversedType,