libmisc: macro.h: Add LM_FOREACH_PARAM

1 files changed, 46 insertions, 0 deletions

diff --git a/libmisc/include/libmisc/macro.h b/libmisc/include/libmisc/macro.h
index d7f6243..a2d4264 100644
--- a/libmisc/include/libmisc/macro.h
+++ b/libmisc/include/libmisc/macro.h
@@ -64,6 +64,9 @@
 #define LM_FIRST(a, ...)        a
 #define LM_SECOND(a, b, ...)    b
 
+#define LM_FIRST_(...)          LM_FIRST(__VA_ARGS__)
+#define LM_SECOND_(...)         LM_SECOND(__VA_ARGS__)
+
 #define LM_EAT(...)
 #define LM_EXPAND(...)          __VA_ARGS__
 
@@ -83,6 +86,25 @@
 
 #define LM_IS_TUPLE(x)          LM_IS_SENTINEL(_LM_IS_TUPLE x)
 #define _LM_IS_TUPLE(...)       LM_SENTINEL()
+/* For LM_IS_EMPTY_TUPLE:
+ *
+ * Given
+ *
+ *     #define HELPER(...) B, __VA_OPT__(C,) D
+ *
+ * then evaluating the sequence of tokens `HELPER x , A` will give us a
+ * new sequence of tokens according to the following table:
+ *
+ *     not a tuple    : HELPER x , A
+ *     tuple, nonempty: B        , C       , D       , A
+ *     tuple, empty   : B        , D       , A
+ *
+ * Looking at this table, it is clear that we must look at the 2nd
+ * resulting comma-separated-value (argument), and set A=false,
+ * C=false, D=true (and B doesn't matter).
+ */
+#define LM_IS_EMPTY_TUPLE(x)    LM_SECOND_(_LM_IS_EMPTY_TUPLE x, LM_F)
+#define _LM_IS_EMPTY_TUPLE(...) bogus, __VA_OPT__(LM_F,) LM_T
 
 /* `tuples` is a sequence of `(tuple1)(tuple2)(tuple3)` */
 #define _LM_TUPLES_COMMA(...)           (__VA_ARGS__),
@@ -105,6 +127,30 @@
 #define _LM_DEFER2(macro) macro LM_EAT LM_EAT()()
 
 /**
+ * LM_FOREACH_PARAM(func, (fixedparams), params...) calls
+ * func(fixedparams..., param) for each param.
+ *
+ * BUG: LM_FOREACH_PARAM is limited to (16*2)-1=31 params.
+ */
+#define LM_FOREACH_PARAM(func, fixedparams, ...) _LM_EVAL(_LM_FOREACH_PARAM(func, fixedparams, __VA_ARGS__))
+#define _LM_FOREACH_PARAM(func, fixedparams, ...) _LM_FOREACH_PARAM_ITEM(func, fixedparams, __VA_ARGS__, ())
+#define _LM_FOREACH_PARAM_FIXEDPARAMS(fixedparams) _LM_FOREACH_PARAM_FIXEDPARAMS_inner fixedparams
+#define _LM_FOREACH_PARAM_FIXEDPARAMS_inner(...) __VA_ARGS__ __VA_OPT__(,)
+#define _LM_FOREACH_PARAM_ITEM(func, fixedparams, param, ...)                                 \
+	LM_IF(LM_IS_EMPTY_TUPLE(param))()(                                                    \
+		_LM_DEFER2(func)(_LM_FOREACH_PARAM_FIXEDPARAMS(fixedparams) param)            \
+		_LM_DEFER2(_LM_FOREACH_PARAM_ITEM_indirect)()(func, fixedparams, __VA_ARGS__) \
+	)
+#define _LM_FOREACH_PARAM_ITEM_indirect() _LM_FOREACH_PARAM_ITEM
+
+/** The same as LM_FOREACH_PARAM(), but callable from inside of LM_FOREACH_PARAM().  */
+#define LM_FOREACH_PARAM2(...) _LM_DEFER2(_LM_FOREACH_PARAM_ITEM_indirect)()(__VA_ARGS__, ())
+
+/** The same as above, but evaluates the arguments first.  */
+#define LM_FOREACH_PARAM_(...) LM_FOREACH_PARAM(__VA_ARGS__)
+#define LM_FOREACH_PARAM2_(...) LM_FOREACH_PARAM2(__VA_ARGS__)
+
+/**
  * LM_FOREACH_TUPLE( (tup1) (tup2) (tup3), func, args...) calls
  * func(args..., tup...) for each tuple.
  *