AMDG
Wong, Shin Guey wrote:
Hi all,
This is my first email to this list; please point me out if I done
anything wrong in this mail like the title format or etc…
I am a newbie to the Boost library. I am really interesting on the
usage of the Boost preprocessor library. I would like to archive 1 of
the thing but I am not sure whether it is possible with Boost
preprocessor library:
Converting the binary number to hexadecimal or decimal value
Eg: BIN2HEX(011) -> 0x3 or BIN2DEC(011) -> 3
BIN2HEX(1111) -> 0xf or BIN2DEC(1111) -> 15
I had read the
C-Template-Metaprogramming-Concepts-Tools-and-Techniques-from-Boost-and-Beyond-C-in-Depth-Series
which tell me how to archive that using template. But what I really
want is to done it with the preprocessor without using any template
which will not affect the run time but only the compile time.
I know that I can use the loop and the arithmetic function from the
Boost library but how do I get the binary number characters count, eg.
COUNT(011) -> 3 or COUNT(0111) -> 4. So that I can use this count with
loop and the arithmetic function to perform the conversion from binary
to hexadecimal or decimal.
You can't implement BIN2DEC(1111) using Boost.Preprocessor
arithmetic. The only way to do it is:
#define BIN2DEC_0 0
#define BIN2DEC_1 1
#define BIN2DEC_11 2
...
#define BIN2DEC_1111 15
...
There is a way to get BIN2HEX(1 1 1 1) for example:
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define BINARY_IS_ONE_IMPL_0
#define BINARY_IS_ONE_IMPL_1
#define BINARY_IS_ONE(x)
BOOST_PP_IS_EMPTY(BOOST_PP_CAT(BINARY_IS_ONE_IMPL_, x))
#define BINARY_POP_FRONT_IMPL_0
#define BINARY_POP_FRONT_IMPL_1
#define BINARY_POP_FRONT_IMPL(x) BOOST_PP_CAT(BINARY_POP_FRONT_IMPL_, x)
#define BINARY_CLEAR(x) EMPTY_BINARY
#define BINARY_POP_FRONT(x) BOOST_PP_IF(BINARY_IS_ONE(x), BINARY_CLEAR,
BINARY_POP_FRONT_IMPL)(x)
#define BINARY_IS_EMPTY_IMPL_EMPTY_BINARY
#define BINARY_IS_EMPTY(x)
BOOST_PP_IS_EMPTY(BOOST_PP_CAT(BINARY_IS_EMPTY_IMPL_, x))
#define BINARY_SIZE_IMPL(n, x) (BINARY_POP_FRONT(BOOST_PP_TUPLE_ELEM(2,
0, x)), n)
#define BINARY_SIZE_IMPL_PRED(n, x)
BOOST_PP_NOT(BINARY_IS_ONE(BOOST_PP_TUPLE_ELEM(2, 0, x)))
#define BINARY_SIZE(x) BOOST_PP_TUPLE_ELEM(2, 1,
BOOST_PP_WHILE(BINARY_SIZE_IMPL_PRED, BINARY_SIZE_IMPL, (x, 1)))
#define BINARY_FRONT_IMPL_0 0, ~
#define BINARY_FRONT_IMPL_1 1, ~
#define BINARY_FRONT_IMPL(x, y) x
#define BINARY_FRONT(x) BOOST_PP_CAT(BINARY_FRONT_IMPL,
(BOOST_PP_CAT(BINARY_FRONT_IMPL_, x)))
#define BINARY_TO_HEX_IMPL_0000 0
#define BINARY_TO_HEX_IMPL_0001 1
#define BINARY_TO_HEX_IMPL_0010 2
#define BINARY_TO_HEX_IMPL_0011 3
#define BINARY_TO_HEX_IMPL_0100 4
#define BINARY_TO_HEX_IMPL_0101 5
#define BINARY_TO_HEX_IMPL_0110 6
#define BINARY_TO_HEX_IMPL_0111 7
#define BINARY_TO_HEX_IMPL_1000 8
#define BINARY_TO_HEX_IMPL_1001 9
#define BINARY_TO_HEX_IMPL_1010 A
#define BINARY_TO_HEX_IMPL_1011 B
#define BINARY_TO_HEX_IMPL_1100 C
#define BINARY_TO_HEX_IMPL_1101 D
#define BINARY_TO_HEX_IMPL_1110 E
#define BINARY_TO_HEX_IMPL_1111 F
#define BINARY_GET1(x) (BINARY_FRONT(x))
#define BINARY_GET2(x) (BINARY_FRONT(x))BINARY_GET1(BINARY_POP_FRONT(x))
#define BINARY_GET3(x) (BINARY_FRONT(x))BINARY_GET2(BINARY_POP_FRONT(x))
#define BINARY_GET4(x) (BINARY_FRONT(x))BINARY_GET3(BINARY_POP_FRONT(x))
#define BINARY_EVAL(x) x
#define BINARY_EMPTY
#define BINARY_POP1(x) BINARY_EVAL(BINARY_POP_FRONT BINARY_EMPTY(x))
#define BINARY_POP2(x) BINARY_POP1(BINARY_POP_FRONT(x))
#define BINARY_POP3(x) BINARY_POP2(BINARY_POP_FRONT(x))
#define BINARY_POP4(x) BINARY_POP3(BINARY_POP_FRONT(x))
#define BINARY_TO_HEX_IMPL(n, result)
(BINARY_POP4(BOOST_PP_TUPLE_ELEM(2, 0, result)),
BOOST_PP_CAT(BOOST_PP_TUPLE_ELEM(2, 1, result),
BOOST_PP_CAT(BINARY_TO_HEX_IMPL_,
BOOST_PP_SEQ_CAT(BINARY_GET4(BOOST_PP_TUPLE_ELEM(2, 0, result))))))
#define BINARY_RESULT(n, result) /**/
#define BINARY_TO_HEX_IMPL_SHORT_CIRCUIT(n, result)
BOOST_PP_IF(BINARY_TO_HEX_PRED(n, result), BINARY_TO_HEX_IMPL,
BINARY_RESULT)(n, result)
#define BINARY_TO_HEX_PRED(n, x)
BOOST_PP_NOT(BINARY_IS_EMPTY(BOOST_PP_TUPLE_ELEM(2, 0, x)))
#define BINARY_PAD_TO_4(x) BOOST_PP_REPEAT(BOOST_PP_MOD(BOOST_PP_SUB(4,
BOOST_PP_MOD(BINARY_SIZE(x), 4)), 4), 0 BOOST_PP_TUPLE_EAT(3), ~) x
#define BINARY_TO_HEX(val) BOOST_PP_TUPLE_ELEM(2, 1,
BOOST_PP_WHILE(BINARY_TO_HEX_PRED, BINARY_TO_HEX_IMPL_SHORT_CIRCUIT,
(BINARY_PAD_TO_4(val), 0x)))
BINARY_TO_HEX(1 0 1 0 0 1)
In Christ,
Steven Watanabe
