eval/fate: try to fix nan printing format failures.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/eval.c

@@ -659,7 +659,11 @@ int main(int argc, char **argv)
         av_expr_parse_and_eval(&d, *expr,
                                const_names, const_values,
                                NULL, NULL, NULL, NULL, NULL, 0, NULL);
-        printf("'%s' -> %f\n\n", *expr, d);
+        if(isnan(d)){
+            printf("'%s' -> nan\n\n", *expr);
+        }else{
+            printf("'%s' -> %f\n\n", *expr, d);
+        }
     }
 
     av_expr_parse_and_eval(&d, "1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)",

tests/ref/fate/eval

@@ -134,7 +134,7 @@ Evaluating 'sqrt(1764)'
 'sqrt(1764)' -> 42.000000
 
 Evaluating 'sqrt(-1)'
-'sqrt(-1)' -> -nan
+'sqrt(-1)' -> nan
 
 Evaluating 'not(1)'
 'not(1)' -> 0.000000
@@ -155,7 +155,7 @@ Evaluating 'PI^1.23'
 'PI^1.23' -> 4.087844
 
 Evaluating 'pow(-1,1.23)'
-'pow(-1,1.23)' -> -nan
+'pow(-1,1.23)' -> nan
 
 12.700000 == 12.7
 0.931323 == 0.931322575