add support for while() loops again ugly syntax while(condition, statements)...

add support for while() loops again ugly syntax while(condition, statements) but very simple implementation

Originally committed as revision 6814 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/eval.c

@@ -133,7 +133,7 @@ struct ff_expr_s {
         e_squish, e_gauss, e_ld,
         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_last, e_st, e_while,
     } type;
     double value; // is sign in other types
     union {
@@ -155,6 +155,12 @@ static double eval_expr(Parser * p, AVEvalExpr * e) {
         case e_squish: return 1/(1+exp(4*eval_expr(p, e->param[0])));
         case e_gauss: { double d = eval_expr(p, e->param[0]); return exp(-d*d/2)/sqrt(2*M_PI); }
         case e_ld:     return e->value * p->var[clip(eval_expr(p, e->param[0]), 0, VARS-1)];
+        case e_while: {
+            double d;
+            while(eval_expr(p, e->param[0]))
+                d=eval_expr(p, e->param[1]);
+            return d;
+        }
         default: {
             double d = eval_expr(p, e->param[0]);
             double d2 = eval_expr(p, e->param[1]);
@@ -266,6 +272,7 @@ static AVEvalExpr * parse_primary(Parser *p) {
     else if( strmatch(next, "lt"    ) ) { AVEvalExpr * tmp = d->param[1]; d->param[1] = d->param[0]; d->param[0] = tmp; d->type = e_gte; }
     else if( strmatch(next, "ld"    ) ) d->type = e_ld;
     else if( strmatch(next, "st"    ) ) d->type = e_st;
+    else if( strmatch(next, "while" ) ) d->type = e_while;
     else {
         for(i=0; p->func1_name && p->func1_name[i]; i++){
             if(strmatch(next, p->func1_name[i])){