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authorKenta Murata <mrkn@mrkn.jp>2020-12-19 04:24:15 +0900
committerKenta Murata <mrkn@mrkn.jp>2020-12-19 22:13:58 +0900
commitff9e40811c67b1090966b655f7adc0684fc58abe (patch)
tree5ade13fabd69840d3ad5f90d089c2044068fd45a /ext/bigdecimal
parent928a06723d1ede495b7c3b42f3ca48e370ccec77 (diff)
[bigdecimal] Add BigDecimal#precision
https://github.com/ruby/bigdecimal/commit/458eb66c49
Diffstat (limited to 'ext/bigdecimal')
-rw-r--r--ext/bigdecimal/bigdecimal.c68
1 files changed, 68 insertions, 0 deletions
diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 039a4d7..ef975a0 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -378,6 +378,73 @@ BigDecimal_prec(VALUE self)
}
/*
+ * call-seq:
+ * big_decimal.precision -> intreger
+ *
+ * Returns the number of decimal digits in this number.
+ *
+ * Example:
+ *
+ * BigDecimal("0").precision # => 0
+ * BigDecimal("1").precision # => 1
+ * BigDecimal("-1e20").precision # => 21
+ * BigDecimal("1e-20").precision # => 20
+ * BigDecimal("Infinity").precision # => 0
+ * BigDecimal("-Infinity").precision # => 0
+ * BigDecimal("NaN").precision # => 0
+ */
+static VALUE
+BigDecimal_precision(VALUE self)
+{
+ ENTER(1);
+
+ Real *p;
+ GUARD_OBJ(p, GetVpValue(self, 1));
+
+ /*
+ * The most significant digit is frac[0], and the least significant digit is frac[Prec-1].
+ * When the exponent is zero, the decimal point is located just before frac[0].
+ * When the exponent is negative, the decimal point moves to leftward.
+ * Conversely, when the exponent is positive, the decimal point moves to rightward.
+ *
+ * | frac[0] frac[1] frac[2] . frac[3] frac[4] ... frac[Prec-1]
+ * |------------------------> exponent == 3
+ */
+
+ ssize_t ex = p->exponent;
+ ssize_t precision;
+ if (ex < 0) {
+ precision = (-ex + 1) * BASE_FIG; /* 1 is for p->frac[0] */
+ ex = 0;
+ }
+ else if (p->Prec > 0) {
+ BDIGIT x = p->frac[0];
+ for (precision = 0; x > 0; x /= 10) {
+ ++precision;
+ }
+ }
+
+ if (ex > (ssize_t)p->Prec) {
+ precision += (ex - 1) * BASE_FIG;
+ }
+ else if (p->Prec > 0) {
+ ssize_t n = (ssize_t)p->Prec - 1;
+ while (n > 0 && p->frac[n] == 0) --n;
+
+ precision += n * BASE_FIG;
+
+ if (ex < (ssize_t)p->Prec) {
+ BDIGIT x = p->frac[n];
+ for (; x > 0 && x % 10 == 0; x /= 10) {
+ --precision;
+ }
+ }
+ }
+
+ return SSIZET2NUM(precision);
+}
+
+/*
* call-seq: hash
*
* Creates a hash for this BigDecimal.
@@ -3509,6 +3576,7 @@ Init_bigdecimal(void)
/* instance methods */
rb_define_method(rb_cBigDecimal, "precs", BigDecimal_prec, 0);
+ rb_define_method(rb_cBigDecimal, "precision", BigDecimal_precision, 0);
rb_define_method(rb_cBigDecimal, "add", BigDecimal_add2, 2);
rb_define_method(rb_cBigDecimal, "sub", BigDecimal_sub2, 2);