1 /* MIT (BSD) license - see LICENSE file for details */
2 #ifndef CCAN_CPPMAGIC_H
3 #define CCAN_CPPMAGIC_H
6 * CPPMAGIC_NOTHING - expands to nothing
8 #define CPPMAGIC_NOTHING()
11 * CPPMAGIC_STRINGIFY - convert arguments to a string literal
13 #define _CPPMAGIC_STRINGIFY(...) #__VA_ARGS__
14 #define CPPMAGIC_STRINGIFY(...) _CPPMAGIC_STRINGIFY(__VA_ARGS__)
17 * CPPMAGIC_GLUE2 - glue arguments together
19 * CPPMAGIC_GLUE2(@a_, @b_)
20 * expands to the expansion of @a_ followed immediately
21 * (combining tokens) by the expansion of @b_
23 #define _CPPMAGIC_GLUE2(a_, b_) a_##b_
24 #define CPPMAGIC_GLUE2(a_, b_) _CPPMAGIC_GLUE2(a_, b_)
27 * CPPMAGIC_1ST - return 1st argument
29 * CPPMAGIC_1ST(@a_, ...)
30 * expands to the expansion of @a_
32 #define CPPMAGIC_1ST(a_, ...) a_
35 * CPPMAGIC_2ND - return 2nd argument
37 * CPPMAGIC_2ST(@a_, @b_, ...)
38 * expands to the expansion of @b_
40 #define CPPMAGIC_2ND(a_, b_, ...) b_
43 * CPPMAGIC_ISZERO - is argument '0'
46 * expands to '1' if @a is '0', otherwise expands to '0'.
48 #define _CPPMAGIC_ISPROBE(...) CPPMAGIC_2ND(__VA_ARGS__, 0)
49 #define _CPPMAGIC_PROBE() $, 1
50 #define _CPPMAGIC_ISZERO_0 _CPPMAGIC_PROBE()
51 #define CPPMAGIC_ISZERO(a_) \
52 _CPPMAGIC_ISPROBE(CPPMAGIC_GLUE2(_CPPMAGIC_ISZERO_, a_))
55 * CPPMAGIC_NONZERO - is argument not '0'
57 * CPPMAGIC_NONZERO(@a)
58 * expands to '0' if @a is '0', otherwise expands to '1'.
60 #define CPPMAGIC_NONZERO(a_) CPPMAGIC_ISZERO(CPPMAGIC_ISZERO(a_))
63 * CPPMAGIC_NONEMPTY - does the macro have any arguments?
67 * CPPMAGIC_NONEMPTY(@a)
68 * CPPMAGIC_NONEMPTY(@a, ...)
71 #define _CPPMAGIC_EOA() 0
72 #define CPPMAGIC_NONEMPTY(...) \
73 CPPMAGIC_NONZERO(CPPMAGIC_1ST(_CPPMAGIC_EOA __VA_ARGS__)())
76 * CPPMAGIC_ISEMPTY - does the macro have no arguments?
80 * CPPMAGIC_ISEMPTY(@a)
81 * CPPMAGIC_ISEMPTY(@a, ...)
84 #define CPPMAGIC_ISEMPTY(...) \
85 CPPMAGIC_ISZERO(CPPMAGIC_NONEMPTY(__VA_ARGS__))
88 * CPPMAGIC_IFELSE - preprocessor conditional
90 * CPPMAGIC_IFELSE(@cond)(@if)(@else)
91 * expands to @else if @cond is '0', otherwise expands to @if
93 #define _CPPMAGIC_IF_0(...) _CPPMAGIC_IF_0_ELSE
94 #define _CPPMAGIC_IF_1(...) __VA_ARGS__ _CPPMAGIC_IF_1_ELSE
95 #define _CPPMAGIC_IF_0_ELSE(...) __VA_ARGS__
96 #define _CPPMAGIC_IF_1_ELSE(...)
97 #define _CPPMAGIC_IFELSE(cond_) CPPMAGIC_GLUE2(_CPPMAGIC_IF_, cond_)
98 #define CPPMAGIC_IFELSE(cond_) \
99 _CPPMAGIC_IFELSE(CPPMAGIC_NONZERO(cond_))
102 * CPPMAGIC_EVAL - force multiple expansion passes
104 * Forces macros in the arguments to be expanded repeatedly (up to
105 * 1024 times) even when CPP would usually stop expanding.
107 #define CPPMAGIC_EVAL1(...) __VA_ARGS__
108 #define CPPMAGIC_EVAL2(...) \
109 CPPMAGIC_EVAL1(CPPMAGIC_EVAL1(__VA_ARGS__))
110 #define CPPMAGIC_EVAL4(...) \
111 CPPMAGIC_EVAL2(CPPMAGIC_EVAL2(__VA_ARGS__))
112 #define CPPMAGIC_EVAL8(...) \
113 CPPMAGIC_EVAL4(CPPMAGIC_EVAL4(__VA_ARGS__))
114 #define CPPMAGIC_EVAL16(...) \
115 CPPMAGIC_EVAL8(CPPMAGIC_EVAL8(__VA_ARGS__))
116 #define CPPMAGIC_EVAL32(...) \
117 CPPMAGIC_EVAL16(CPPMAGIC_EVAL16(__VA_ARGS__))
118 #define CPPMAGIC_EVAL64(...) \
119 CPPMAGIC_EVAL32(CPPMAGIC_EVAL32(__VA_ARGS__))
120 #define CPPMAGIC_EVAL128(...) \
121 CPPMAGIC_EVAL64(CPPMAGIC_EVAL64(__VA_ARGS__))
122 #define CPPMAGIC_EVAL256(...) \
123 CPPMAGIC_EVAL128(CPPMAGIC_EVAL128(__VA_ARGS__))
124 #define CPPMAGIC_EVAL512(...) \
125 CPPMAGIC_EVAL256(CPPMAGIC_EVAL256(__VA_ARGS__))
126 #define CPPMAGIC_EVAL1024(...) \
127 CPPMAGIC_EVAL512(CPPMAGIC_EVAL512(__VA_ARGS__))
128 #define CPPMAGIC_EVAL(...) CPPMAGIC_EVAL1024(__VA_ARGS__)
131 * CPPMAGIC_DEFER1, CPPMAGIC_DEFER2 - defer expansion
133 #define CPPMAGIC_DEFER1(a_) a_ CPPMAGIC_NOTHING()
134 #define CPPMAGIC_DEFER2(a_) a_ CPPMAGIC_NOTHING CPPMAGIC_NOTHING()()
137 * CPPMAGIC_MAP - iterate another macro across arguments
138 * @m: name of a one argument macro
140 * CPPMAGIC_MAP(@m, @a1, @a2, ... @an)
141 * expands to the expansion of @m(@a1) , @m(@a2) , ... , @m(@an)
143 #define _CPPMAGIC_MAP_() _CPPMAGIC_MAP
144 #define _CPPMAGIC_MAP(m_, a_, ...) \
146 CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__)) \
147 (, CPPMAGIC_DEFER2(_CPPMAGIC_MAP_)()(m_, __VA_ARGS__)) \
149 #define CPPMAGIC_MAP(m_, ...) \
150 CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__)) \
151 (CPPMAGIC_EVAL(_CPPMAGIC_MAP(m_, __VA_ARGS__))) \
155 * CPPMAGIC_2MAP - iterate another macro across pairs of arguments
156 * @m: name of a two argument macro
158 * CPPMAGIC_2MAP(@m, @a1, @b1, @a2, @b2, ..., @an, @bn)
159 * expands to the expansion of
160 * @m(@a1, @b1) , @m(@a2, @b2) , ... , @m(@an, @bn)
162 #define _CPPMAGIC_2MAP_() _CPPMAGIC_2MAP
163 #define _CPPMAGIC_2MAP(m_, a_, b_, ...) \
165 CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__)) \
166 (, CPPMAGIC_DEFER2(_CPPMAGIC_2MAP_)()(m_, __VA_ARGS__)) \
168 #define CPPMAGIC_2MAP(m_, ...) \
169 CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__)) \
170 (CPPMAGIC_EVAL(_CPPMAGIC_2MAP(m_, __VA_ARGS__))) \
174 * CPPMAGIC_JOIN - separate arguments with given delimiter
177 * CPPMAGIC_JOIN(@d, @a1, @a2, ..., @an)
178 * expands to the expansion of @a1 @d @a2 @d ... @d @an
180 #define _CPPMAGIC_JOIN_() _CPPMAGIC_JOIN
181 #define _CPPMAGIC_JOIN(d_, a_, ...) \
183 CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__)) \
184 (d_ CPPMAGIC_DEFER2(_CPPMAGIC_JOIN_)()(d_, __VA_ARGS__)) \
186 #define CPPMAGIC_JOIN(d_, ...) \
187 CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__)) \
188 (CPPMAGIC_EVAL(_CPPMAGIC_JOIN(d_, __VA_ARGS__))) \
191 #endif /* CCAN_CPPMAGIC_H */