numeric.c: int_truncate

* numeric.c (int_truncate): add an optional parameter, digits, as
  well as Integer#round.  [Feature #12245]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54624 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Mon Apr 18 12:55:31 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* numeric.c (int_truncate): add an optional parameter, digits, as
+	  well as Integer#round.  [Feature #12245]
+
 Sun Apr 17 04:18:56 2016  CHIKANAGA Tomoyuki  <nagachika@ruby-lang.org>
 
 	* tool/redmine-backporter.rb: revisions are strings.

NEWS

@@ -43,8 +43,8 @@ with all sufficient information, see the ChangeLog file or Redmine
 
 * Integer
 
-  * Integer#ceil and Integer#floor now take an optional digits, as well
-    as Integer#round.  [Feature #12245]
+  * Integer#ceil, Integer#floor, and Integer#truncate now take an optional
+    digits, as well as Integer#round.  [Feature #12245]
 
 * String
 

numeric.c

@@ -1935,6 +1935,36 @@ rb_int_ceil(VALUE num, int ndigits)
     return rb_int_plus(num, rb_int_minus(f, rb_int_modulo(num, f)));
 }
 
+VALUE
+rb_int_truncate(VALUE num, int ndigits)
+{
+    VALUE f;
+    VALUE m;
+
+    if (int_round_zero_p(num, ndigits))
+	return INT2FIX(0);
+    f = int_pow(10, -ndigits);
+    if (FIXNUM_P(num) && FIXNUM_P(f)) {
+	SIGNED_VALUE x = FIX2LONG(num), y = FIX2LONG(f);
+	int neg = x < 0;
+	if (neg) x = -x;
+	x = x / y * y;
+	if (neg) x = -x;
+	return LONG2NUM(x);
+    }
+    if (RB_TYPE_P(f, T_FLOAT)) {
+	/* then int_pow overflow */
+	return INT2FIX(0);
+    }
+    m = rb_int_modulo(num, f);
+    if (int_neg_p(num)) {
+	return rb_int_plus(num, rb_int_minus(f, m));
+    }
+    else {
+	return rb_int_minus(num, m);
+    }
+}
+
 /*
  *  call-seq:
  *     float.round([ndigits])  ->  integer or float
@@ -2817,7 +2847,7 @@ rb_num2ull(VALUE val)
  *
  *  As +int+ is already an Integer, all these methods simply return the receiver.
  *
- *  Synonyms are #to_int, #truncate.
+ *  Synonyms is #to_int
  */
 
 static VALUE
@@ -4346,6 +4376,37 @@ int_ceil(int argc, VALUE* argv, VALUE num)
     return rb_int_ceil(num, ndigits);
 }
 
+/*
+ *  call-seq:
+ *     int.truncate([ndigits])  ->  integer or float
+ *
+ *  Returns the smallest number than or equal to +int+ in decimal
+ *  digits (default 0 digits).
+ *
+ *  Precision may be negative.  Returns a floating point number when +ndigits+
+ *  is positive, +self+ for zero, and truncate up for negative.
+ *
+ *     1.truncate        #=> 1
+ *     1.truncate(2)     #=> 1.0
+ *     15.truncate(-1)   #=> 10
+ */
+
+static VALUE
+int_truncate(int argc, VALUE* argv, VALUE num)
+{
+    int ndigits;
+
+    if (!rb_check_arity(argc, 0, 1)) return num;
+    ndigits = NUM2INT(argv[0]);
+    if (ndigits > 0) {
+	return rb_Float(num);
+    }
+    if (ndigits == 0) {
+	return num;
+    }
+    return rb_int_truncate(num, ndigits);
+}
+
 /*
  *  Document-class: ZeroDivisionError
  *
@@ -4518,7 +4579,7 @@ Init_Numeric(void)
     rb_define_method(rb_cInteger, "to_f", int_to_f, 0);
     rb_define_method(rb_cInteger, "floor", int_floor, -1);
     rb_define_method(rb_cInteger, "ceil", int_ceil, -1);
-    rb_define_method(rb_cInteger, "truncate", int_to_i, 0);
+    rb_define_method(rb_cInteger, "truncate", int_truncate, -1);
     rb_define_method(rb_cInteger, "round", int_round, -1);
     rb_define_method(rb_cInteger, "<=>", int_cmp, 1);
 

test/ruby/test_integer.rb

@@ -249,6 +249,31 @@ class TestInteger < Test::Unit::TestCase
     assert_int_equal(-1111_1111_1111_1111_1111_1111_1111_1110, (-1111_1111_1111_1111_1111_1111_1111_1111).ceil(-1))
   end
 
+  def test_truncate
+    assert_int_equal(11111, 11111.truncate)
+    assert_int_equal(11111, 11111.truncate(0))
+
+    assert_float_equal(11111.0, 11111.truncate(1))
+    assert_float_equal(11111.0, 11111.truncate(2))
+
+    assert_int_equal(11110, 11110.truncate(-1))
+    assert_int_equal(11110, 11119.truncate(-1))
+    assert_int_equal(11100, 11100.truncate(-2))
+    assert_int_equal(11100, 11199.truncate(-2))
+    assert_int_equal(0, 11111.truncate(-5))
+    assert_int_equal(+200, +299.truncate(-2))
+    assert_int_equal(+300, +300.truncate(-2))
+    assert_int_equal(-200, -299.truncate(-2))
+    assert_int_equal(-300, -300.truncate(-2))
+    assert_int_equal(+20 * 10**70, (+25 * 10**70).truncate(-71))
+    assert_int_equal(-20 * 10**70, (-25 * 10**70).truncate(-71))
+    assert_int_equal(+20 * 10**70, (+25 * 10**70 - 1).truncate(-71))
+    assert_int_equal(-20 * 10**70, (-25 * 10**70 + 1).truncate(-71))
+
+    assert_int_equal(1111_1111_1111_1111_1111_1111_1111_1110, 1111_1111_1111_1111_1111_1111_1111_1111.truncate(-1))
+    assert_int_equal(-1111_1111_1111_1111_1111_1111_1111_1110, (-1111_1111_1111_1111_1111_1111_1111_1111).truncate(-1))
+  end
+
   def test_bitwise_and_with_integer_mimic_object
     def (obj = Object.new).to_int
       10