builtin: Implement min/max builtin function (#48)

This CL implementation is not 100% accurate since,
keyfunc and default value parameter is not supported.

We can support it later CL.

Author: corona10

builtin/builtin.go

@@ -47,8 +47,8 @@ func init() {
 		// py.MustNewMethod("iter", builtin_iter, 0, iter_doc),
 		py.MustNewMethod("len", builtin_len, 0, len_doc),
 		py.MustNewMethod("locals", py.InternalMethodLocals, 0, locals_doc),
-		// py.MustNewMethod("max", builtin_max, 0, max_doc),
-		// py.MustNewMethod("min", builtin_min, 0, min_doc),
+		py.MustNewMethod("max", builtin_max, 0, max_doc),
+		py.MustNewMethod("min", builtin_min, 0, min_doc),
 		py.MustNewMethod("next", builtin_next, 0, next_doc),
 		py.MustNewMethod("open", builtin_open, 0, open_doc),
 		// py.MustNewMethod("oct", builtin_oct, 0, oct_doc),
@@ -772,6 +772,135 @@ func builtin_len(self, v py.Object) (py.Object, error) {
 	return py.Len(v)
 }
 
+const max_doc = `
+max(iterable, *[, default=obj, key=func]) -> value
+max(arg1, arg2, *args, *[, key=func]) -> value
+
+With a single iterable argument, return its biggest item. The
+default keyword-only argument specifies an object to return if
+the provided iterable is empty.
+With two or more arguments, return the largest argument.`
+
+func builtin_max(self py.Object, args py.Tuple, kwargs py.StringDict) (py.Object, error) {
+	return min_max(args, kwargs, "max")
+}
+
+const min_doc = `
+min(iterable, *[, default=obj, key=func]) -> value
+min(arg1, arg2, *args, *[, key=func]) -> value
+
+With a single iterable argument, return its smallest item. The
+default keyword-only argument specifies an object to return if
+the provided iterable is empty.
+With two or more arguments, return the smallest argument.`
+
+func builtin_min(self py.Object, args py.Tuple, kwargs py.StringDict) (py.Object, error) {
+	return min_max(args, kwargs, "min")
+}
+
+func min_max(args py.Tuple, kwargs py.StringDict, name string) (py.Object, error) {
+	kwlist := []string{"key", "default"}
+	positional := len(args)
+	var format string
+	var values py.Object
+	var cmp func(a py.Object, b py.Object) (py.Object, error)
+	if name == "min" {
+		format = "|$OO:min"
+		cmp = py.Le
+	} else if name == "max" {
+		format = "|$OO:max"
+		cmp = py.Ge
+	}
+	var defaultValue py.Object
+	var keyFunc py.Object
+	var maxVal, maxItem py.Object
+	var kf *py.Function
+
+	if positional > 1 {
+		values = args
+	} else {
+		err := py.UnpackTuple(args, nil, name, 1, 1, &values)
+		if err != nil {
+			return nil, err
+		}
+	}
+	err := py.ParseTupleAndKeywords(nil, kwargs, format, kwlist, &keyFunc, &defaultValue)
+	if err != nil {
+		return nil, err
+	}
+	if keyFunc == py.None {
+		keyFunc = nil
+	}
+	if keyFunc != nil {
+		var ok bool
+		kf, ok = keyFunc.(*py.Function)
+		if !ok {
+			return nil, py.ExceptionNewf(py.TypeError, "'%s' object is not callable", keyFunc.Type())
+		}
+	}
+	if defaultValue != nil {
+		maxItem = defaultValue
+		if keyFunc != nil {
+			maxVal, err = py.Call(kf, py.Tuple{defaultValue}, nil)
+			if err != nil {
+				return nil, err
+			}
+		} else {
+			maxVal = defaultValue
+		}
+	}
+	iter, err := py.Iter(values)
+	if err != nil {
+		return nil, err
+	}
+
+	for {
+		item, err := py.Next(iter)
+		if err != nil {
+			if py.IsException(py.StopIteration, err) {
+				break
+			}
+			return nil, err
+		}
+		if maxVal == nil {
+			if keyFunc != nil {
+				maxVal, err = py.Call(kf, py.Tuple{item}, nil)
+				if err != nil {
+					return nil, err
+				}
+			} else {
+				maxVal = item
+			}
+			maxItem = item
+		} else {
+			var compareVal py.Object
+			if keyFunc != nil {
+				compareVal, err = py.Call(kf, py.Tuple{item}, nil)
+				if err != nil {
+					return nil, err
+				}
+			} else {
+				compareVal = item
+			}
+			changed, err := cmp(compareVal, maxVal)
+			if err != nil {
+				return nil, err
+			}
+			if changed == py.True {
+				maxVal = compareVal
+				maxItem = item
+			}
+		}
+
+	}
+
+	if maxItem == nil {
+		return nil, py.ExceptionNewf(py.ValueError, "%s() arg is an empty sequence", name)
+	}
+
+	return maxItem, nil
+}
+
 const chr_doc = `chr(i) -> Unicode character
 
 Return a Unicode string of one character with ordinal i; 0 <= i <= 0x10ffff.`

builtin/tests/builtin.py

@@ -75,6 +75,63 @@ def fn(x):
     assert locals()["x"] == 1
 fn(1)
 
+def func(p):
+   return p[1]
+
+doc="min"
+values = (1,2,3)
+v = min(values)
+assert v == 1
+v = min(4,5,6)
+assert v == 4
+v = min((), default=-1)
+assert v == -1
+v = min([], default=-1)
+assert v == -1
+v = min([], key=func, default=(1,3))
+assert v == (1,3)
+v = min([(1,3), (2,1)], key=func)
+assert v == (2,1)
+ok = False
+try:
+    min([(1,3), (2,1)], key=3)
+except TypeError:
+    ok = True
+assert ok, "TypeError not raised"
+ok = False
+try:
+    min([])
+except ValueError:
+    ok = True
+assert ok, "ValueError not raised"
+
+doc="max"
+values = (1,2,3)
+v = max(values)
+assert v == 3
+v = max(4,5,6)
+assert v == 6
+v = max((), default=-1)
+assert v == -1
+v = max([], default=-1)
+assert v == -1
+v = max([], key=func, default=(1,3))
+assert v == (1,3)
+v = max([(1,3), (2,1)], key=func)
+assert v == (1,3)
+ok = False
+try:
+    max([(1,3), (2,1)], key=3)
+except TypeError:
+    ok = True
+assert ok, "TypeError not raised"
+ok = False
+try:
+    max([])
+except ValueError:
+    ok = True
+assert ok, "ValueError not raised"
+
 doc="next no default"
 def gen():
     yield 1

py/args.go

@@ -417,11 +417,16 @@ func ParseTupleAndKeywords(args Tuple, kwargs StringDict, format string, kwlist
 		return ExceptionNewf(TypeError, "Internal error: supply the same number of results and kwlist")
 	}
 	min, max, name, ops := parseFormat(format)
+	keywordOnly := false
 	err := checkNumberOfArgs(name, len(args)+len(kwargs), len(results), min, max)
 	if err != nil {
 		return err
 	}
 
+	if len(ops) > 0 && ops[0] == "$" {
+		keywordOnly = true
+		ops = ops[1:]
+	}
 	// Check all the kwargs are in kwlist
 	// O(N^2) Slow but kwlist is usually short
 	for kwargName := range kwargs {
@@ -442,10 +447,10 @@ func ParseTupleAndKeywords(args Tuple, kwargs StringDict, format string, kwlist
 				return ExceptionNewf(TypeError, "%s() got multiple values for argument '%s'", name, kw)
 			}
 			args = append(args, value)
+		} else if keywordOnly {
+			args = append(args, nil)
 		}
-
 	}
-
 	for i, arg := range args {
 		op := ops[i]
 		result := results[i]