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"goto" for tail recursion changed to "while"

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This commit is contained in:
Roberto Ierusalimschy 1999-01-04 15:34:49 -02:00
parent d7294c6de8
commit f5bc671030
1 changed files with 13 additions and 14 deletions
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27
lbuiltin.c
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@ -1,5 +1,5 @@
/*
** $Id: lbuiltin.c,v 1.43 1998/12/30 13:16:50 roberto Exp $
** $Id: lbuiltin.c,v 1.44 1999/01/04 12:55:09 roberto Exp roberto $
** Built-in functions
** See Copyright Notice in lua.h
*/
@ -445,21 +445,20 @@ static int sort_comp (TObject *f, TObject *a, TObject *b) {
}
static void auxsort (Hash *a, int l, int u, TObject *f) {
init: /* using goto's to optimize tail recursion */
if (u <= l) return; /* 0 or 1 element */
else {
while (l < u) { /* for tail recursion */
TObject *P;
int i, j;
/* sort elements a[l], a[(l+u)/2] and a[u] */
if (sort_comp(f, luaH_getint(a, u), luaH_getint(a, l))) /* a[l]>a[u]? */
swap(a, l, u);
if (u-l == 1) return; /* only 2 elements */
if (u-l == 1) break; /* only 2 elements */
i = (l+u)/2;
if (sort_comp(f, luaH_getint(a, i), luaH_getint(a, l))) /* a[l]>a[i]? */
P = luaH_getint(a, i);
if (sort_comp(f, P, luaH_getint(a, l))) /* a[l]>a[i]? */
swap(a, l, i);
else if (sort_comp(f, luaH_getint(a, u), luaH_getint(a, i))) /* a[i]>a[u]? */
else if (sort_comp(f, luaH_getint(a, u), P)) /* a[i]>a[u]? */
swap(a, i, u);
if (u-l == 2) return; /* only 3 elements */
if (u-l == 2) break; /* only 3 elements */
P = L->stack.top++;
*P = *luaH_getint(a, i); /* save pivot on stack (for GC) */
swap(a, i, u-1); /* put median element as pivot (a[u-1]) */
@ -477,15 +476,15 @@ static void auxsort (Hash *a, int l, int u, TObject *f) {
swap(a, u-1, i); /* swap pivot (a[u-1]) with a[i] */
L->stack.top--; /* remove pivot from stack */
/* a[l..i-1] <= a[i] == P <= a[i+1..u] */
if (i-l < u-i) { /* check which "half" is bigger */
auxsort(a, l, i-1, f); /* call recursively the smaller one */
l = i+1; goto init; /* auxsort(a, i+1, u, f); */
/* adjust so that smaller "half" is in [j..i] and larger one in [l..u] */
if (i-l < u-i) {
j=l; i=i-1; l=i+2;
}
else {
auxsort(a, i+1, u, f);
u = i-1; goto init; /* auxsort(a, l, i-1, f); */
j=i+1; i=u; u=j-2;
}
}
auxsort(a, j, i, f); /* call recursively the smaller one */
} /* repeat the routine for the larger one */
}
static void luaB_sort (void) {