晋太元中,武陵人捕鱼为业。缘溪行,忘路之远近。忽逢桃花林,夹岸数百步,中无杂树,芳草鲜美,落英缤纷。渔人甚异之,复前行,欲穷其林。 林尽水源,便得一山,山有小口,仿佛若有光。便舍船,从口入。初极狭,才通人。复行数十步,豁然开朗。土地平旷,屋舍俨然,有良田、美池、桑竹之属。阡陌交通,鸡犬相闻。其中往来种作,男女衣着,悉如外人。黄发垂髫,并怡然自乐。 见渔人,乃大惊,问所从来。具答之。便要还家,设酒杀鸡作食。村中闻有此人,咸来问讯。自云先世避秦时乱,率妻子邑人来此绝境,不复出焉,遂与外人间隔。问今是何世,乃不知有汉,无论魏晋。此人一一为具言所闻,皆叹惋。余人各复延至其家,皆出酒食。停数日,辞去。此中人语云:“不足为外人道也。”(间隔 一作:隔绝) 既出,得其船,便扶向路,处处志之。及郡下,诣太守,说如此。太守即遣人随其往,寻向所志,遂迷,不复得路。 南阳刘子骥,高尚士也,闻之,欣然规往。未果,寻病终。后遂无问津者。
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Copyright 1999, 2001-2017 Free Software Foundation, Inc. Contributed by the AriC and Caramba projects, INRIA. This file is part of the GNU MPFR Library. The GNU MPFR Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. The GNU MPFR Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. ############################################################################## Known bugs: * The overflow/underflow exceptions may be badly handled in some functions; specially when the intermediary internal results have exponent which exceeds the hardware limit (2^30 for a 32 bits CPU, and 2^62 for a 64 bits CPU) or the exact result is close to an overflow/underflow threshold. * Under Linux/x86 with the traditional FPU, some functions do not work if the FPU rounding precision has been changed to single (this is a bad practice and should be useless, but one never knows what other software will do). * Some functions do not use MPFR_SAVE_EXPO_* macros, thus do not behave correctly in a reduced exponent range. * Function hypot gives incorrect result when on the one hand the difference between parameters' exponents is near 2*MPFR_EMAX_MAX and on the other hand the output precision or the precision of the parameter with greatest absolute value is greater than 2*MPFR_EMAX_MAX-4. Potential bugs: * Possible incorrect results due to internal underflow, which can lead to a huge loss of accuracy while the error analysis doesn't take that into account. If the underflow occurs at the last function call (just before the MPFR_CAN_ROUND), the result should be correct (or MPFR gets into an infinite loop). TODO: check the code and the error analysis. * Possible integer overflows on some machines. * Possible bugs with huge precisions (> 2^30). * Possible bugs if the chosen exponent range does not allow to represent the range [1/16, 16]. * Possible infinite loop in some functions for particular cases: when the exact result is an exactly representable number or the middle of consecutive two such numbers. However for non-algebraic functions, it is believed that no such case exists, except the well-known cases like cos(0)=1, exp(0)=1, and so on, and the x^y function when y is an integer or y=1/2^k. * The mpfr_set_ld function may be quite slow if the long double type has an exponent of more than 15 bits. * mpfr_set_d may give wrong results on some non-IEEE architectures. * Error analysis for some functions may be incorrect (out-of-date due to modifications in the code?). * Possible use of non-portable feature (pre-C99) of the integer division with negative result.