[FFmpeg-devel] [PATCH] eval: add mathematical constants (PI, E, PHI).

[Nicolas George]

Signed-off-by: Nicolas George <nicolas.george at normalesup.org>
---
 doc/eval.texi    |   10 ++++++++++
 libavutil/eval.c |   18 ++++++++++++++++++
 2 files changed, 28 insertions(+), 0 deletions(-)


If this is accepted, I can submit patches to remove them from the various
places where they are implemented as variables.


diff --git a/doc/eval.texi b/doc/eval.texi
index b41f31e..18d8487 100644
--- a/doc/eval.texi
+++ b/doc/eval.texi
@@ -99,6 +99,16 @@ Return the greatest common divisor of @var{x} and @var{y}. If both @var{x} and
 @var{y} are 0 or either or both are less than zero then behavior is undefined.
 @end table
 
+The following constants are available:
+ at table @option
+ at item PI
+area of the unit disc, approximatively 3.14
+ at item E
+exp(1) (Euler's number), approximatively 2.718
+ at item PHI
+golden ratio (1+sqrt(5))/2, approximatively 1.618
+ at end table
+
 Note that:
 
 @code{*} works like AND
diff --git a/libavutil/eval.c b/libavutil/eval.c
index 0c61ad0..3a8b60d 100644
--- a/libavutil/eval.c
+++ b/libavutil/eval.c
@@ -72,6 +72,15 @@ static const int8_t si_prefixes['z' - 'E' + 1] = {
     ['Y'-'E']=  24,
 };
 
+static const struct {
+    const char *name;
+    double value;
+} constants[] = {
+    { "E",   M_E   },
+    { "PI",  M_PI  },
+    { "PHI", M_PHI },
+};
+
 double av_strtod(const char *numstr, char **tail)
 {
     double d;
@@ -233,6 +242,15 @@ static int parse_primary(AVExpr **e, Parser *p)
             return 0;
         }
     }
+    for (i = 0; i < FF_ARRAY_ELEMS(constants); i++) {
+        if (strmatch(p->s, constants[i].name)) {
+            p->s += strlen(constants[i].name);
+            d->type = e_value;
+            d->value = constants[i].value;
+            *e = d;
+            return 0;
+        }
+    }
 
     p->s= strchr(p->s, '(');
     if (p->s==NULL) {
-- 
1.7.6.3