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lavu/eval: add if() and ifnot() eval functions
They allow to implement the if/then/else logic, which cannot be implemented otherwise. For example the expression: A*B + not(A)*C always evaluates to NaN if B is NaN, even in the case where A is 0.
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@ -98,6 +98,14 @@ point (@var{x}, @var{y}) from the origin.
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@item gcd(x, y)
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Return the greatest common divisor of @var{x} and @var{y}. If both @var{x} and
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@var{y} are 0 or either or both are less than zero then behavior is undefined.
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@item if(x, y)
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Evaluate @var{x}, and if the result is non-zero return the result of
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the evaluation of @var{y}, return 0 otherwise.
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@item ifnot(x, y)
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Evaluate @var{x}, and if the result is zero return the result of the
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evaluation of @var{y}, return 0 otherwise.
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@end table
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The following constants are available:
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@ -116,13 +124,13 @@ Note that:
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@code{+} works like OR
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thus
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and the construct:
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@example
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if A then B else C
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@end example
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is equivalent to
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@example
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A*B + not(A)*C
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if(A,B) + ifnot(A,C)
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@end example
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In your C code, you can extend the list of unary and binary functions,
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@ -155,7 +155,7 @@
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#define LIBAVUTIL_VERSION_MAJOR 51
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#define LIBAVUTIL_VERSION_MINOR 34
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#define LIBAVUTIL_VERSION_MICRO 100
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#define LIBAVUTIL_VERSION_MICRO 101
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#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
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LIBAVUTIL_VERSION_MINOR, \
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@ -136,6 +136,7 @@ struct AVExpr {
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e_pow, e_mul, e_div, e_add,
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e_last, e_st, e_while, e_floor, e_ceil, e_trunc,
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e_sqrt, e_not, e_random, e_hypot, e_gcd,
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e_if, e_ifnot,
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} type;
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double value; // is sign in other types
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union {
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@ -165,6 +166,8 @@ static double eval_expr(Parser *p, AVExpr *e)
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case e_trunc: return e->value * trunc(eval_expr(p, e->param[0]));
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case e_sqrt: return e->value * sqrt (eval_expr(p, e->param[0]));
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case e_not: return e->value * (eval_expr(p, e->param[0]) == 0);
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case e_if: return e->value * ( eval_expr(p, e->param[0]) ? eval_expr(p, e->param[1]) : 0);
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case e_ifnot: return e->value * (!eval_expr(p, e->param[0]) ? eval_expr(p, e->param[1]) : 0);
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case e_random:{
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int idx= av_clip(eval_expr(p, e->param[0]), 0, VARS-1);
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uint64_t r= isnan(p->var[idx]) ? 0 : p->var[idx];
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@ -324,6 +327,8 @@ static int parse_primary(AVExpr **e, Parser *p)
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else if (strmatch(next, "random")) d->type = e_random;
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else if (strmatch(next, "hypot" )) d->type = e_hypot;
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else if (strmatch(next, "gcd" )) d->type = e_gcd;
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else if (strmatch(next, "if" )) d->type = e_if;
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else if (strmatch(next, "ifnot" )) d->type = e_ifnot;
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else {
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for (i=0; p->func1_names && p->func1_names[i]; i++) {
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if (strmatch(next, p->func1_names[i])) {
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@ -690,6 +695,9 @@ int main(int argc, char **argv)
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"pow(PI,1.23)",
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"PI^1.23",
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"pow(-1,1.23)",
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"if(1, 2)",
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"ifnot(0, 23)",
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"ifnot(1, NaN) + if(0, 1)",
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NULL
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};
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@ -160,5 +160,14 @@ Evaluating 'PI^1.23'
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Evaluating 'pow(-1,1.23)'
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'pow(-1,1.23)' -> nan
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Evaluating 'if(1, 2)'
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'if(1, 2)' -> 2.000000
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Evaluating 'ifnot(0, 23)'
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'ifnot(0, 23)' -> 23.000000
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Evaluating 'ifnot(1, NaN) + if(0, 1)'
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'ifnot(1, NaN) + if(0, 1)' -> 0.000000
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12.700000 == 12.7
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0.931323 == 0.931322575
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