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eval: implement not() expression

This commit is contained in:
Stefano Sabatini 2011-05-23 13:13:50 +02:00
parent cf06e3e4dd
commit 3c2c52baec
3 changed files with 11 additions and 7 deletions
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8
doc/eval.texi
View File

@ -76,6 +76,9 @@ integer. For example, "trunc(-1.5)" is "-1.0".
@item sqrt(expr)
Compute the square root of @var{expr}. This is equivalent to
"(@var{expr})^.5".
@item not(expr)
Return 1.0 if @var{expr} is zero, 0.0 otherwise.
@end table
Note that:
@ -93,11 +96,6 @@ is equivalent to
A*B + not(A)*C
@end example
When A evaluates to either 1 or 0, that is the same as
@example
A*B + eq(A,0)*C
@end example
In your C code, you can extend the list of unary and binary functions,
and define recognized constants, so that they are available for your
expressions.

2
libavutil/avutil.h
View File

@ -41,7 +41,7 @@
#define LIBAVUTIL_VERSION_MAJOR 51
#define LIBAVUTIL_VERSION_MINOR 2
#define LIBAVUTIL_VERSION_MICRO 1
#define LIBAVUTIL_VERSION_MICRO 2
#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
LIBAVUTIL_VERSION_MINOR, \

8
libavutil/eval.c
View File

@ -125,7 +125,7 @@ struct AVExpr {
e_mod, e_max, e_min, e_eq, e_gt, e_gte,
e_pow, e_mul, e_div, e_add,
e_last, e_st, e_while, e_floor, e_ceil, e_trunc,
e_sqrt,
e_sqrt, e_not,
} type;
double value; // is sign in other types
union {
@ -153,6 +153,7 @@ static double eval_expr(Parser *p, AVExpr *e)
case e_ceil : return e->value * ceil (eval_expr(p, e->param[0]));
case e_trunc: return e->value * trunc(eval_expr(p, e->param[0]));
case e_sqrt: return e->value * sqrt (eval_expr(p, e->param[0]));
case e_not: return e->value * eval_expr(p, e->param[0]) == 0;
case e_while: {
double d = NAN;
while (eval_expr(p, e->param[0]))
@ -288,6 +289,7 @@ static int parse_primary(AVExpr **e, Parser *p)
else if (strmatch(next, "ceil" )) d->type = e_ceil;
else if (strmatch(next, "trunc" )) d->type = e_trunc;
else if (strmatch(next, "sqrt" )) d->type = e_sqrt;
else if (strmatch(next, "not" )) d->type = e_not;
else {
for (i=0; p->func1_names && p->func1_names[i]; i++) {
if (strmatch(next, p->func1_names[i])) {
@ -456,6 +458,7 @@ static int verify_expr(AVExpr *e)
case e_ceil:
case e_trunc:
case e_sqrt:
case e_not:
return verify_expr(e->param[0]);
default: return verify_expr(e->param[0]) && verify_expr(e->param[1]);
}
@ -637,6 +640,9 @@ int main(void)
"ceil(-123.123)",
"sqrt(1764)",
"sqrt(-1)",
"not(1)",
"not(NAN)",
"not(0)",
NULL
};