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Improve castNode notation by introducing list-extraction-specific variants.

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This extends the castNode() notation introduced by commit 5bcab1114 to
provide, in one step, extraction of a list cell's pointer and coercion to
a concrete node type.  For example, "lfirst_node(Foo, lc)" is the same
as "castNode(Foo, lfirst(lc))".  Almost half of the uses of castNode
that have appeared so far include a list extraction call, so this is
pretty widely useful, and it saves a few more keystrokes compared to the
old way.

As with the previous patch, back-patch the addition of these macros to
pg_list.h, so that the notation will be available when back-patching.

Patch by me, after an idea of Andrew Gierth's.

Discussion: https://postgr.es/m/14197.1491841216@sss.pgh.pa.us
This commit is contained in:
Tom Lane 2017-04-10 13:51:29 -04:00
parent c0a493e17c
commit be182d5702
1 changed files with 7 additions and 0 deletions
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7
src/include/nodes/pg_list.h
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@ -106,26 +106,32 @@ list_length(const List *l)
#define lfirst(lc) ((lc)->data.ptr_value)
#define lfirst_int(lc) ((lc)->data.int_value)
#define lfirst_oid(lc) ((lc)->data.oid_value)
#define lfirst_node(type,lc) castNode(type, lfirst(lc))
#define linitial(l) lfirst(list_head(l))
#define linitial_int(l) lfirst_int(list_head(l))
#define linitial_oid(l) lfirst_oid(list_head(l))
#define linitial_node(type,l) castNode(type, linitial(l))
#define lsecond(l) lfirst(lnext(list_head(l)))
#define lsecond_int(l) lfirst_int(lnext(list_head(l)))
#define lsecond_oid(l) lfirst_oid(lnext(list_head(l)))
#define lsecond_node(type,l) castNode(type, lsecond(l))
#define lthird(l) lfirst(lnext(lnext(list_head(l))))
#define lthird_int(l) lfirst_int(lnext(lnext(list_head(l))))
#define lthird_oid(l) lfirst_oid(lnext(lnext(list_head(l))))
#define lthird_node(type,l) castNode(type, lthird(l))
#define lfourth(l) lfirst(lnext(lnext(lnext(list_head(l)))))
#define lfourth_int(l) lfirst_int(lnext(lnext(lnext(list_head(l)))))
#define lfourth_oid(l) lfirst_oid(lnext(lnext(lnext(list_head(l)))))
#define lfourth_node(type,l) castNode(type, lfourth(l))
#define llast(l) lfirst(list_tail(l))
#define llast_int(l) lfirst_int(list_tail(l))
#define llast_oid(l) lfirst_oid(list_tail(l))
#define llast_node(type,l) castNode(type, llast(l))
/*
* Convenience macros for building fixed-length lists
@ -204,6 +210,7 @@ extern ListCell *list_nth_cell(const List *list, int n);
extern void *list_nth(const List *list, int n);
extern int list_nth_int(const List *list, int n);
extern Oid list_nth_oid(const List *list, int n);
#define list_nth_node(type,list,n) castNode(type, list_nth(list, n))
extern bool list_member(const List *list, const void *datum);
extern bool list_member_ptr(const List *list, const void *datum);