diff options
Diffstat (limited to 'math.c')
| -rw-r--r-- | math.c | 62 |
1 files changed, 41 insertions, 21 deletions
@@ -474,7 +474,6 @@ math_exp(VALUE unused_obj, VALUE x) # define M_LN10 2.30258509299404568401799145468436421 #endif -static double math_log1(VALUE x); FUNC_MINIMIZED(static VALUE math_log(int, const VALUE *, VALUE)); /* @@ -509,20 +508,6 @@ math_log(int argc, const VALUE *argv, VALUE unused_obj) return rb_math_log(argc, argv); } -VALUE -rb_math_log(int argc, const VALUE *argv) -{ - VALUE x, base; - double d; - - rb_scan_args(argc, argv, "11", &x, &base); - d = math_log1(x); - if (argc == 2) { - d /= math_log1(base); - } - return DBL2NUM(d); -} - static double get_double_rshift(VALUE x, size_t *pnumbits) { @@ -541,16 +526,51 @@ get_double_rshift(VALUE x, size_t *pnumbits) } static double -math_log1(VALUE x) +math_log_split(VALUE x, size_t *numbits) { - size_t numbits; - double d = get_double_rshift(x, &numbits); + double d = get_double_rshift(x, numbits); domain_check_min(d, 0.0, "log"); - /* check for pole error */ - if (d == 0.0) return -HUGE_VAL; + return d; +} + +#if defined(log2) || defined(HAVE_LOG2) +# define log_intermediate log2 +#else +# define log_intermediate log10 +#endif + +VALUE +rb_math_log(int argc, const VALUE *argv) +{ + VALUE x, base; + double d; + size_t numbits; - return log(d) + numbits * M_LN2; /* log(d * 2 ** numbits) */ + argc = rb_scan_args(argc, argv, "11", &x, &base); + d = math_log_split(x, &numbits); + if (argc == 2) { + size_t numbits_2; + double b = math_log_split(base, &numbits_2); + /* check for pole error */ + if (d == 0.0) { + if (b > 0.0) return DBL2NUM(HUGE_VAL); + if (b < 0.0) return DBL2NUM(-HUGE_VAL); + return DBL2NUM(nan("")); + } + else if (b == 0.0) { + return DBL2NUM(-0.0); + } + d = log_intermediate(d) / log_intermediate(b); + numbits -= numbits_2; + } + else { + /* check for pole error */ + if (d == 0.0) return DBL2NUM(-HUGE_VAL); + d = log(d); + } + d += numbits * M_LN2; + return DBL2NUM(d); } #ifndef log2 |