学步园

下面复杂的过程模拟编译器的推到过程。

BOOST的预处理十分复杂。真是非常难以理清楚。下面的内容只能算作笔记，避免忘记了。</p> <p>也只有自己能看明白了。<br /> // push_back_.cpp : 定义控制台应用程序的入口点。<br /> //<br /> #include "stdafx.h"<br /> #include <iostream><br /> #define seq (a) (b) (c)<br /> int _tmain(int argc, _TCHAR* argv[])<br /> { </p> <p> return 0;<br /> }<br /> // VC6 1200<br /> // VC7 1300<br /> // VC8 1400<br /> // VC9 1500<br /> # define BOOST_PP_CAT(a, b) BOOST_PP_CAT_OO((a, b))<br /> # define BOOST_PP_CAT_OO(par) BOOST_PP_CAT_I ## par<br /> # define BOOST_PP_CAT_I(a, b) a ## b<br /> # define BOOST_PP_SEQ_CAT(seq) /<br /> BOOST_PP_IF( /<br /> BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(seq)), /<br /> BOOST_PP_SEQ_CAT_I, /<br /> BOOST_PP_SEQ_HEAD(seq) BOOST_PP_TUPLE_EAT_1 /<br /> )(seq) /<br /> /**/<br /> //seq是一个带括弧的序列，如上面定义的#define seq (a) (b) (c)<br /> # define BOOST_PP_SEQ_SIZE(seq) BOOST_PP_SEQ_SIZE_I(seq)<br /> # define BOOST_PP_SEQ_SIZE_I(seq) BOOST_PP_CAT(BOOST_PP_SEQ_SIZE_, BOOST_PP_SEQ_SIZE_0 seq)<br /> //上面 BOOST_PP_CAT()括弧里面( BOOST_PPSEQ_SIZE_, BOOST_PP_SEQ_SIZE_0 seq),先对BOOST_PP_SEQ_SIZE_0进行扩展<br /> //也就是BOOST_PP_SIZE_0 (a) (b) (c) 这是宏调用不是宏定义，对空格不敏感。<br /> //先执行BOOST_PP_SIZE_0 (a) 为 BOOST_PP_SEQ_SIZE_1<br /> //再扩展BOOST_PP_SEQ_SIZE_1 (b) 为 BOOST_PP_SEQ_SIZE_2<br /> //在扩展BOOST_PP_SEQ_SIZE_2 (c) 为 BOOST_PP_SEQ_SIZE_3<br /> //上面再用BOOST_PP_CAT(BOOST_PP_SEQ_SIZE_, BOOST_PPSEQ_SIZE_3)连接起来，成为：<br /> //BOOST_PP_SEQ_SIZE_BOOST_PPSEQ_SIZE_3,<br /> //而它的值为 3,就是这个序列的有三个元素的意思。<br /> # define BOOST_PP_SEQ_SIZE_0(_) BOOST_PP_SEQ_SIZE_1<br /> # define BOOST_PP_SEQ_SIZE_1(_) BOOST_PP_SEQ_SIZE_2<br /> # define BOOST_PP_SEQ_SIZE_2(_) BOOST_PP_SEQ_SIZE_3<br /> # define BOOST_PP_SEQ_SIZE_BOOST_PP_SEQ_SIZE_3 3<br /> # define BOOST_PP_DEC(x) BOOST_PP_DEC_OO((x))<br /> # define BOOST_PP_DEC_OO(par) BOOST_PP_DEC_I ## par<br /> # define BOOST_PP_DEC_I(x) BOOST_PP_DEC_ ## x<br /> # define BOOST_PP_DEC_0 0<br /> # define BOOST_PP_DEC_3 2 //上面的BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(seq)) 最终结果是 2<br /> # define BOOST_PP_SEQ_HEAD(seq) BOOST_PP_SEQ_ELEM(0, seq) //最终得到的是首元素。<br /> //宏调用的时候不会理会是否有空格。<br /> //宏定义就不会忽略是否有空格。<br /> # define BOOST_PP_SEQ_ELEM(i, seq) BOOST_PP_SEQ_ELEM_I((i, seq))//这儿的i而序列的下标，可以得到序列的任何一个元素。<br /> # define BOOST_PP_SEQ_ELEM_I(i, seq) BOOST_PP_SEQ_ELEM_II((BOOST_PP_SEQ_ELEM_ ## i seq))<br /> # define BOOST_PP_SEQ_ELEM_II(res) BOOST_PP_SEQ_ELEM_IV(BOOST_PP_SEQ_ELEM_III res)<br /> # define BOOST_PP_SEQ_ELEM_III(x, _) x BOOST_PP_EMPTY()//最终得到的是x<br /> # define BOOST_PP_SEQ_ELEM_IV(x) x<br /> # define BOOST_PP_EMPTY()<br /> # define BOOST_PP_SEQ_ELEM_0(x) x, BOOST_PP_NIL//BOOST_PP_NIL只是一个符号，像占位符一样的功能。<br /> # define BOOST_PP_SEQ_CAT_I(seq) BOOST_PP_SEQ_FOLD_LEFT(BOOST_PP_SEQ_CAT_O, BOOST_PP_SEQ_HEAD(seq), BOOST_PP_SEQ_TAIL(seq))<br /> //上面展开的部分结构是：<br /> BOOST_PP_IF( 2, BOOST_PP_SEQ_CAT_I, a BOOST_PP_TUPLE_EAT_1 )(seq)<br /> # define BOOST_PP_IF(cond, t, f) BOOST_PP_IF_I(cond, t, f)<br /> # define BOOST_PP_IF_I(cond, t, f) BOOST_PP_IIF(BOOST_PP_BOOL(cond), t, f)<br /> # define BOOST_PP_BOOL(x) BOOST_PP_BOOL_OO((x))<br /> # define BOOST_PP_BOOL_OO(par) BOOST_PP_BOOL_I ## par<br /> # define BOOST_PP_BOOL_I(x) BOOST_PP_BOOL_ ## x<br /> # define BOOST_PP_BOOL_2 1 //BOOST_PP_BOOL(2)的值为1<br /> # define BOOST_PP_IIF(bit, t, f) BOOST_PP_IIF_OO((bit, t, f))<br /> # define BOOST_PP_IIF_OO(par) BOOST_PP_IIF_I ## par<br /> # define BOOST_PP_IIF_I(bit, t, f) BOOST_PP_IIF_ ## bit(t, f)<br /> # define BOOST_PP_IIF_0(t, f) f //false 选f<br /> # define BOOST_PP_IIF_1(t, f) t //true 选 t<br /> //因此BOOST_PP_IF( 2, BOOST_PP_SEQ_CAT_I, a BOOST_PP_TUPLE_EAT_1 )(seq) 推导的结果是：<br /> BOOST_PP_SEQ_CAT_I(seq)<br /> # define BOOST_PP_SEQ_CAT_I(seq) BOOST_PP_SEQ_FOLD_LEFT(BOOST_PP_SEQ_CAT_O, BOOST_PP_SEQ_HEAD(seq), BOOST_PP_SEQ_TAIL(seq))<br /> //BOOST_PP_SEQ_TAIL(seq)是除第一个元素外余下的元素。<br /> # define BOOST_PP_SEQ_TAIL(seq) BOOST_PP_SEQ_TAIL_ID(BOOST_PP_SEQ_TAIL_I seq)<br /> # define BOOST_PP_SEQ_TAIL_ID(id) id<br /> # define BOOST_PP_SEQ_TAIL_I(x)<br /> # define BOOST_PP_SEQ_FOLD_LEFT BOOST_PP_CAT(BOOST_PP_SEQ_FOLD_LEFT_, BOOST_PP_AUTO_REC(BOOST_PP_SEQ_FOLD_LEFT_P, 256))<br /> # define BOOST_PP_AUTO_REC(pred, n) BOOST_PP_NODE_ENTRY_ ## n(pred)<br /> # define BOOST_PP_NODE_ENTRY_256(p) BOOST_PP_NODE_128(p)(p)(p)(p)(p)(p)(p)(p)<br /> # define BOOST_PP_NODE_128(p) BOOST_PP_IIF(p(128), BOOST_PP_NODE_64, BOOST_PP_NODE_192)<br /> # define BOOST_PP_SEQ_FOLD_LEFT_P(n) BOOST_PP_CAT(BOOST_PP_SEQ_FOLD_LEFT_CHECK_, BOOST_PP_SEQ_FOLD_LEFT_I_ ## n(BOOST_PP_SEQ_FOLD_LEFT_O, BOOST_PP_NIL, (nil), 1))<br /> # define BOOST_PP_SEQ_FOLD_LEFT_256(op, st, ss) BOOST_PP_SEQ_FOLD_LEFT_I_256(op, st, ss, BOOST_PP_SEQ_SIZE(ss))<br /> # define BOOST_PP_SEQ_FOLD_LEFT_CHECK_BOOST_PP_SEQ_FOLD_LEFT_I_256(op, st, ss, sz) 0<br /> //BOOST_PP_LESS_EQUAL(2,3)<br /> # define BOOST_PP_LESS_EQUAL(x, y) BOOST_PP_LESS_EQUAL_I(x, y)<br /> # define BOOST_PP_LESS_EQUAL_I(x, y) BOOST_PP_NOT(BOOST_PP_SUB(x, y))<br /> # define BOOST_PP_SUB(x, y) BOOST_PP_SUB_I(x, y)<br /> # define BOOST_PP_SUB_I(x, y) BOOST_PP_TUPLE_ELEM(2, 0, BOOST_PP_WHILE(BOOST_PP_SUB_P, BOOST_PP_SUB_O, (x, y)))<br /> //2_<br /> BOOST_PP_TUPLE_ELEM(2,0,BOOST_PP_WHILE(BOOST_PP_SUB_P,BOOST_PP_SUB_O,(2,3)))<br /> //%%%%%<br /> BOOST_PP_TUPLE_ELEM(2,0,(0,0))<br /> 为: 0<br /> //1_<br /> # define BOOST_PP_WHILE BOOST_PP_CAT(BOOST_PP_WHILE_, BOOST_PP_AUTO_REC(BOOST_PP_WHILE_P, 256))<br /> # define BOOST_PP_AUTO_REC(pred, n) BOOST_PP_NODE_ENTRY_ ## n(pred)<br /> BOOST_PP_NODE_ENTRY_256(BOOST_PP_WHILE_P)<br /> # define BOOST_PP_NODE_ENTRY_256(p) BOOST_PP_NODE_128(p)(p)(p)(p)(p)(p)(p)(p)<br /> BOOST_PP_NODE_128(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)<br /> # define BOOST_PP_NODE_128(p) BOOST_PP_IIF(p(128), BOOST_PP_NODE_64, BOOST_PP_NODE_192)<br /> //XX<br /> BOOST_PP_IIF(BOOST_PP_WHILE_P(128), BOOST_PP_NODE_64, BOOST_PP_NODE_192)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)<br /> //BOOST_PP_WHILE_P(128)<br /> # define BOOST_PP_WHILE_P(n) BOOST_PP_BITAND(BOOST_PP_CAT(BOOST_PP_WHILE_CHECK_, BOOST_PP_WHILE_ ## n(BOOST_PP_WHILE_F, BOOST_PP_NIL, BOOST_PP_NIL)), BOOST_PP_CAT(BOOST_PP_LIST_FOLD_LEFT_CHECK_, BOOST_PP_LIST_FOLD_LEFT_ ## n(BOOST_PP_NIL, BOOST_PP_NIL, BOOST_PP_NIL)))<br /> BOOST_PP_BITAND(BOOST_PP_CAT(BOOST_PP_WHILE_CHECK_, BOOST_PP_WHILE_128(BOOST_PP_WHILE_F, BOOST_PP_NIL, BOOST_PP_NIL)), BOOST_PP_CAT(BOOST_PP_LIST_FOLD_LEFT_CHECK_, BOOST_PP_LIST_FOLD_LEFT_128(BOOST_PP_NIL, BOOST_PP_NIL, BOOST_PP_NIL)))//这儿推断有错误。<br /> //BOOST_PP_WHILE_128<br /> # define BOOST_PP_WHILE_128(p, o, s) BOOST_PP_WHILE_128_C(BOOST_PP_BOOL(p##(129, s)), p, o, s)<br /> BOOST_PP_WHILE_128_C(BOOST_PP_BOOL(BOOST_PP_WHILE_F(129,BOOST_PP_NIL),BOOST_PP_WHILE_F,BOOST_PP_NIL,BOOST_PP_NIL))<br /> # define BOOST_PP_WHILE_F(d, _) 0<br /> BOOST_PP_WHILE_128_C(0,BOOST_PP_WHILE_F,BOOST_PP_NIL,BOOST_PP_NIL))<br /> # define BOOST_PP_WHILE_128_C(c, p, o, s) BOOST_PP_IIF(c, BOOST_PP_WHILE_129, s BOOST_PP_TUPLE_EAT_3)(p, o, BOOST_PP_IIF(c, o, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(129, s))<br /> BOOST_PP_IIF(0, BOOST_PP_WHILE_129, s BOOST_PP_TUPLE_EAT_3)(p, o, BOOST_PP_IIF(c, o, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(129, s))<br /> BOOST_PP_NIL BOOST_PP_TUPLE_EAT_3(BOOST_PP_WHILE_F,BOOST_PP_NIL,BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2(129,BOOST_PP_NIL))<br /> # define BOOST_PP_TUPLE_EAT_2(a, b)<br /> BOOST_PP_NIL BOOST_PP_TUPLE_EAT_3(BOOST_PP_WHILE_F,BOOST_PP_NIL,BOOST_PP_NIL)<br /> # define BOOST_PP_TUPLE_EAT_3(a, b, c)<br /> BOOST_PP_NIL//这一节的最后结果<br /> //at BOOST_PP_WHILE_128<br /> BOOST_PP_BITAND(BOOST_PP_CAT(BOOST_PP_WHILE_CHECK_, BOOST_PP_NIL), BOOST_PP_CAT(BOOST_PP_LIST_FOLD_LEFT_CHECK_, BOOST_PP_LIST_FOLD_LEFT_128(BOOST_PP_NIL, BOOST_PP_NIL, BOOST_PP_NIL)))//<br /> # define BOOST_PP_LIST_FOLD_LEFT_128(o, s, l) BOOST_PP_IIF(BOOST_PP_LIST_IS_CONS(l), BOOST_PP_LIST_FOLD_LEFT_129, s BOOST_PP_TUPLE_EAT_3)(o, BOOST_PP_EXPR_IIF(BOOST_PP_LIST_IS_CONS(l), o)(129, s, BOOST_PP_LIST_FIRST(l)), BOOST_PP_LIST_REST(l))<br /> BOOST_PP_IIF(BOOST_PP_LIST_IS_CONS(BOOST_PP_NIL), BOOST_PP_LIST_FOLD_LEFT_129, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_3)(BOOST_PP_NIL, BOOST_PP_EXPR_IIF(BOOST_PP_LIST_IS_CONS(BOOST_PP_NIL), BOOST_PP_NIL)(129, BOOST_PP_NIL, BOOST_PP_LIST_FIRST(BOOST_PP_NIL)), BOOST_PP_LIST_REST(BOOST_PP_NIL))<br /> # define BOOST_PP_LIST_IS_CONS(list) BOOST_PP_IS_BINARY(list)<br /> # define BOOST_PP_IS_BINARY(x) BOOST_PP_IS_BINARY_I(x)<br /> # define BOOST_PP_IS_BINARY_I(x) BOOST_PP_CHECK(x, BOOST_PP_IS_BINARY_CHECK)<br /> BOOST_PP_CHECK(BOOST_PP_NIL, BOOST_PP_IS_BINARY_CHECK)<br /> # define BOOST_PP_CHECK(x, type) BOOST_PP_CHECK_OO((x, type))<br /> # define BOOST_PP_CHECK_OO(par) BOOST_PP_CHECK_D ## par<br /> BOOST_PP_CHECK_D(BOOST_PP_NIL, BOOST_PP_IS_BINARY_CHECK)<br /> # define BOOST_PP_CHECK_D(x, type) BOOST_PP_CHECK_1(type x)<br /> # define BOOST_PP_CHECK_1(chk) BOOST_PP_CHECK_2(chk)<br /> # define BOOST_PP_CHECK_2(chk) BOOST_PP_CHECK_3((BOOST_PP_CHECK_RESULT_ ## chk))<br /> BOOST_PP_CHECK_3((BOOST_PP_CHECK_RESULT_BOOST_PP_IS_BINARY_CHECK BOOST_PP_NIL))<br /> # define BOOST_PP_CHECK_RESULT_BOOST_PP_IS_BINARY_CHECK 0, BOOST_PP_NIL<br /> BOOST_PP_CHECK_3(( 0, BOOST_PP_NIL BOOST_PP_NIL))<br /> # define BOOST_PP_CHECK_3(im) BOOST_PP_CHECK_5(BOOST_PP_CHECK_4 im)<br /> BOOST_PP_CHECK_5(BOOST_PP_CHECK_4( 0, BOOST_PP_NIL BOOST_PP_NIL) )<br /> # define BOOST_PP_CHECK_4(res, _) res<br /> # define BOOST_PP_CHECK_5(res) res<br /> //最后为 0<br /> BOOST_PP_IIF(0, BOOST_PP_LIST_FOLD_LEFT_129, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_3)(BOOST_PP_NIL, BOOST_PP_EXPR_IIF(0, BOOST_PP_NIL)(129, BOOST_PP_NIL, BOOST_PP_LIST_FIRST(BOOST_PP_NIL)), BOOST_PP_LIST_REST(BOOST_PP_NIL))<br /> # define BOOST_PP_EXPR_IF(cond, expr) BOOST_PP_EXPR_IF_I(cond, expr)<br /> # define BOOST_PP_EXPR_IF_I(cond, expr) BOOST_PP_EXPR_IIF(0, BOOST_PP_NIL)<br /> BOOST_PP_EXPR_IIF(0, BOOST_PP_NIL)<br /> # define BOOST_PP_EXPR_IIF(bit, expr) BOOST_PP_EXPR_IIF_OO((bit, expr))<br /> # define BOOST_PP_EXPR_IIF_OO(par) BOOST_PP_EXPR_IIF_I ## par<br /> BOOST_PP_EXPR_IIF_I(0, BOOST_PP_NIL)<br /> # define BOOST_PP_EXPR_IIF_I(bit, expr) BOOST_PP_EXPR_IIF_ ## bit(expr)<br /> BOOST_PP_EXPR_IIF_0(BOOST_PP_NIL)<br /> # define BOOST_PP_EXPR_IIF_0(expr)<br /> # define BOOST_PP_EXPR_IIF_1(expr) expr<br /> BOOST_PP_IIF(0, BOOST_PP_LIST_FOLD_LEFT_129, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_3)(BOOST_PP_NIL, (129, BOOST_PP_NIL, BOOST_PP_LIST_FIRST(BOOST_PP_NIL)), BOOST_PP_LIST_REST(BOOST_PP_NIL))<br /> BOOST_PP_NIL BOOST_PP_TUPLE_EAT_3(BOOST_PP_NIL, (129, BOOST_PP_NIL, BOOST_PP_LIST_FIRST(BOOST_PP_NIL)), BOOST_PP_LIST_REST(BOOST_PP_NIL)))<br /> # define BOOST_PP_TUPLE_EAT_3(a, b, c)<br /> //推出为：<br /> BOOST_PP_NIL<br /> BOOST_PP_BITAND(BOOST_PP_CAT(BOOST_PP_WHILE_CHECK_, BOOST_PP_NIL), BOOST_PP_CAT(BOOST_PP_LIST_FOLD_LEFT_CHECK_, BOOST_PP_NIL))//<br /> BOOST_PP_BITAND(BOOST_PP_WHILE_CHECK_BOOST_PP_NIL, BOOST_PP_LIST_FOLD_LEFT_CHECK_BOOST_PP_NIL)<br /> # define BOOST_PP_WHILE_CHECK_BOOST_PP_NIL 1<br /> # define BOOST_PP_LIST_FOLD_LEFT_CHECK_BOOST_PP_NIL 1<br /> # define BOOST_PP_BITAND_I(x, y) BOOST_PP_BITAND_ ## x ## y<br /> BOOST_PP_BITAND_I(1,1) BOOST_PP_BITAND_11<br /> # define BOOST_PP_BITAND_11 1<br /> //这儿的结果为：<br /> 1<br /> // at XX<br /> BOOST_PP_NODE_64(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)(BOOST_PP_WHILE_P)<br /> # define BOOST_PP_NODE_1(p) BOOST_PP_IIF(p(1), 1, 2)<br /> //因此 at 2_<br /> BOOST_PP_TUPLE_ELEM(2,0,BOOST_PP_WHILE_1(BOOST_PP_SUB_P,BOOST_PP_SUB_O,(2,3)))<br /> # define BOOST_PP_WHILE_1(p, o, s) BOOST_PP_WHILE_1_C(BOOST_PP_BOOL(p(2, s)), p, o, s)<br /> BOOST_PP_WHILE_1_C(BOOST_PP_BOOL(BOOST_PP_SUB_P(2,(2,3)),BOOST_PP_SUB_P,BOOST_PP_SUB_O),(2,3))<br /> # define BOOST_PP_SUB_P(d, xy) BOOST_PP_TUPLE_ELEM(2, 1, xy)<br /> BOOST_PP_TUPLE_ELEM(2,1,(2,3))<br /> # define BOOST_PP_SUB_P(d, xy) BOOST_PP_TUPLE_ELEM(2, 1, xy)<br /> BOOST_PP_TUPLE_ELEM(2,1,(2,3))<br /> # define BOOST_PP_TUPLE_ELEM(size, index, tuple) BOOST_PP_TUPLE_ELEM_OO((size, index, tuple))<br /> # define BOOST_PP_TUPLE_ELEM_OO(par) BOOST_PP_TUPLE_ELEM_I ## par<br /> BOOST_PP_TUPLE_ELEM_OO((2,1,(2,3)))<br /> BOOST_PP_TUPLE_ELEM_I(2,1,(2,3))<br /> # define BOOST_PP_TUPLE_ELEM_I(s, i, t) BOOST_PP_TUPLE_ELEM_II(BOOST_PP_TUPLE_ELEM_ ## s ## _ ## i t)<br /> # define BOOST_PP_TUPLE_ELEM_II(res) res<br /> BOOST_PP_TUPLE_ELEM_II(BOOST_PP_TUPLE_ELEM_2_1(2,3))<br /> BOOST_PP_TUPLE_ELEM_2_1(2,3)<br /> # define BOOST_PP_TUPLE_ELEM_2_1(a, b) b<br /> 3<br /> # define BOOST_PP_BOOL(x) BOOST_PP_BOOL_OO((x))<br /> # define BOOST_PP_BOOL_OO(par) BOOST_PP_BOOL_I ## par<br /> # define BOOST_PP_BOOL_3 1<br /> BOOST_PP_WHILE_1_C(1,BOOST_PP_SUB_P,BOOST_PP_SUB_O,(2,3))<br /> # define BOOST_PP_WHILE_1_C(c, p, o, s) BOOST_PP_IIF(c, BOOST_PP_WHILE_2, s BOOST_PP_TUPLE_EAT_3)(p, o, BOOST_PP_IIF(c, o, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(2, s))<br /> BOOST_PP_IIF(1, BOOST_PP_WHILE_2, (2,3) BOOST_PP_TUPLE_EAT_3)(BOOST_PP_SUB_P, BOOST_PP_SUB_O, BOOST_PP_IIF(1, BOOST_PP_SUB_O, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(2, (2,3)))<br /> BOOST_PP_WHILE_2(BOOST_PP_SUB_P, BOOST_PP_SUB_O,BOOST_PP_SUB_O(2, (2,3)))<br /> # define BOOST_PP_SUB_O(d, xy) BOOST_PP_SUB_O_I(BOOST_PP_TUPLE_ELEM(2, 0, xy), BOOST_PP_TUPLE_ELEM(2, 1, xy))<br /> BOOST_PP_SUB_O_I(BOOST_PP_TUPLE_ELEM(2,0,(2,3)),BOOST_PP_TUPLE_ELEM(2, 1, (2,3)))<br /> BOOST_PP_SUB_O_I(2,3)<br /> # define BOOST_PP_SUB_O_I(x, y) (BOOST_PP_DEC(x), BOOST_PP_DEC(y))<br /> (1,2)<br /> BOOST_PP_WHILE_2(BOOST_PP_SUB_P, BOOST_PP_SUB_O,(1,2))<br /> # define BOOST_PP_WHILE_2(p, o, s) BOOST_PP_WHILE_2_C(BOOST_PP_BOOL(p(3, s)), p, o, s)<br /> BOOST_PP_WHILE_2_C(BOOST_PP_BOOL(BOOST_PP_SUB_P(3, (1,2))), BOOST_PP_SUB_P, BOOST_PP_SUB_O, (1,2))<br /> # define BOOST_PP_SUB_P(d, xy) BOOST_PP_TUPLE_ELEM(2, 1, xy)<br /> BOOST_PP_TUPLE_ELEM(2,1,(1,2))<br /> # define BOOST_PP_TUPLE_ELEM(size, index, tuple) BOOST_PP_TUPLE_ELEM_OO((size, index, tuple))<br /> # define BOOST_PP_TUPLE_ELEM_OO(par) BOOST_PP_TUPLE_ELEM_I ## par<br /> BOOST_PP_TUPLE_ELEM_OO((2,1,(1,2)))<br /> BOOST_PP_TUPLE_ELEM_I(2,1,(1,2))<br /> # define BOOST_PP_TUPLE_ELEM_I(s, i, t) BOOST_PP_TUPLE_ELEM_II(BOOST_PP_TUPLE_ELEM_ ## s ## _ ## i t)<br /> # define BOOST_PP_TUPLE_ELEM_II(res) res<br /> BOOST_PP_TUPLE_ELEM_II(BOOST_PP_TUPLE_ELEM_2_1(1,2))<br /> BOOST_PP_TUPLE_ELEM_2_1(1,2)<br /> # define BOOST_PP_TUPLE_ELEM_2_1(a, b) b<br /> 2<br /> BOOST_PP_WHILE_2_C(1, BOOST_PP_SUB_P, BOOST_PP_SUB_O, (1,2))<br /> # define BOOST_PP_WHILE_2_C(c, p, o, s) BOOST_PP_IIF(c, BOOST_PP_WHILE_3, s BOOST_PP_TUPLE_EAT_3)(p, o, BOOST_PP_IIF(c, o, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(3, s))<br /> BOOST_PP_IIF(1, BOOST_PP_WHILE_3, (1,2) BOOST_PP_TUPLE_EAT_3)(BOOST_PP_SUB_P, BOOST_PP_SUB_O, BOOST_PP_IIF(1, BOOST_PP_SUB_O, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(3, (1,2)))<br /> BOOST_PP_WHILE_3(BOOST_PP_SUB_P, BOOST_PP_SUB_O,BOOST_PP_SUB_O(3, (1,2)))<br /> # define BOOST_PP_SUB_O(d, xy) BOOST_PP_SUB_O_I(BOOST_PP_TUPLE_ELEM(2, 0, xy), BOOST_PP_TUPLE_ELEM(2, 1, xy))<br /> BOOST_PP_SUB_O_I(BOOST_PP_TUPLE_ELEM(2,0,(1,2)), BOOST_PP_TUPLE_ELEM(2,1,(1,2)))<br /> BOOST_PP_SUB_O_I(1,2)<br /> # define BOOST_PP_SUB_O_I(x, y) (BOOST_PP_DEC(x), BOOST_PP_DEC(y))<br /> (0,1)<br /> BOOST_PP_WHILE_3(BOOST_PP_SUB_P, BOOST_PP_SUB_O,(0,1))<br /> # define BOOST_PP_WHILE_3(p, o, s) BOOST_PP_WHILE_3_C(BOOST_PP_BOOL(p(4, s)), p, o, s)<br /> BOOST_PP_WHILE_3_C(BOOST_PP_BOOL(BOOST_PP_SUB_P(4, (0,1))), BOOST_PP_SUB_P, BOOST_PP_SUB_O, (0,1))<br /> # define BOOST_PP_SUB_P(d, xy) BOOST_PP_TUPLE_ELEM(2, 1, xy)<br /> BOOST_PP_TUPLE_ELEM(2,1,(0,1))<br /> BOOST_PP_TUPLE_ELEM(2,1,(0,1))<br /> # define BOOST_PP_TUPLE_ELEM(size, index, tuple) BOOST_PP_TUPLE_ELEM_OO((size, index, tuple))<br /> # define BOOST_PP_TUPLE_ELEM_OO(par) BOOST_PP_TUPLE_ELEM_I ## par<br /> BOOST_PP_TUPLE_ELEM_OO((2,1,(0,1)))<br /> BOOST_PP_TUPLE_ELEM_I(2,1,(0,1))<br /> # define BOOST_PP_TUPLE_ELEM_I(s, i, t) BOOST_PP_TUPLE_ELEM_II(BOOST_PP_TUPLE_ELEM_ ## s ## _ ## i t)<br /> # define BOOST_PP_TUPLE_ELEM_II(res) res<br /> BOOST_PP_TUPLE_ELEM_II(BOOST_PP_TUPLE_ELEM_2_1(0,1))<br /> BOOST_PP_TUPLE_ELEM_2_1(0,1)<br /> # define BOOST_PP_TUPLE_ELEM_2_1(a, b) b<br /> 1<br /> BOOST_PP_WHILE_3_C(BOOST_PP_BOOL(1), BOOST_PP_SUB_P, BOOST_PP_SUB_O, (0,1))<br /> BOOST_PP_WHILE_3_C(1, BOOST_PP_SUB_P, BOOST_PP_SUB_O, (0,1))<br /> # define BOOST_PP_WHILE_3_C(c, p, o, s) BOOST_PP_IIF(c, BOOST_PP_WHILE_4, s BOOST_PP_TUPLE_EAT_3)(p, o, BOOST_PP_IIF(c, o, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(4, s))<br /> BOOST_PP_IIF(1, BOOST_PP_WHILE_4, (0,1) BOOST_PP_TUPLE_EAT_3)(BOOST_PP_SUB_P, BOOST_PP_SUB_O, BOOST_PP_IIF(1, BOOST_PP_SUB_O, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(4, (0,1)))<br /> BOOST_PP_WHILE_4(BOOST_PP_SUB_P, BOOST_PP_SUB_O, BOOST_PP_SUB_O(4, (0,1)))<br /> # define BOOST_PP_SUB_O(d, xy) BOOST_PP_SUB_O_I(BOOST_PP_TUPLE_ELEM(2, 0, (0,1)), BOOST_PP_TUPLE_ELEM(2, 1, (0,1)))<br /> BOOST_PP_SUB_O_I(1, 1)<br /> (0,0)<br /> BOOST_PP_WHILE_4(BOOST_PP_SUB_P, BOOST_PP_SUB_O, (0,0))<br /> # define BOOST_PP_WHILE_4(p, o, s) BOOST_PP_WHILE_4_C(BOOST_PP_BOOL(p(5, s)), p, o, s)<br /> BOOST_PP_WHILE_4_C(0, BOOST_PP_SUB_P, BOOST_PP_SUB_O, (0,0))<br /> # define BOOST_PP_WHILE_4(p, o, s) BOOST_PP_WHILE_4_C(BOOST_PP_BOOL(p(5, s)), p, o, s)<br /> BOOST_PP_WHILE_4_C(BOOST_PP_BOOL(BOOST_PP_SUB_P(5, (0,0))), BOOST_PP_SUB_P, BOOST_PP_SUB_O, (0,0))<br /> BOOST_PP_WHILE_4_C(0, BOOST_PP_SUB_P, BOOST_PP_SUB_O, (0,0))<br /> # define BOOST_PP_WHILE_4_C(c, p, o, s) BOOST_PP_IIF(c, BOOST_PP_WHILE_5, s BOOST_PP_TUPLE_EAT_3)(p, o, BOOST_PP_IIF(c, o, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(5, s))<br /> BOOST_PP_IIF(0, BOOST_PP_WHILE_5, (0,0) BOOST_PP_TUPLE_EAT_3)(BOOST_PP_SUB_P, BOOST_PP_SUB_O, BOOST_PP_IIF(0, BOOST_PP_SUB_O, BOOST_PP_NIL BOOST_PP_TUPLE_EAT_2)(5, (0,0)))<br /> //最后结果是：<br /> (0,0)