@@ -55,7 +55,7 @@ typedef struct Parser{

     double (**func2)(void *, double a, double b); // NULL terminated

     char **func2_name;          // NULL terminated

     void *opaque;

-    char **error;

+    const char **error;

 #define VARS 10

     double var[VARS];

 } Parser;

@@ -379,7 +379,7 @@ static int verify_expr(AVEvalExpr * e) {

 AVEvalExpr * ff_parse(char *s, const char **const_name,

                double (**func1)(void *, double), const char **func1_name,

                double (**func2)(void *, double, double), char **func2_name,

-               char **error){

+               const char **error){

     Parser p;

     AVEvalExpr * e;

     char w[strlen(s) + 1], * wp = w;

@@ -416,7 +416,7 @@ double ff_parse_eval(AVEvalExpr * e, double *const_value, void *opaque) {

 double ff_eval2(char *s, double *const_value, const char **const_name,

                double (**func1)(void *, double), const char **func1_name,

                double (**func2)(void *, double, double), char **func2_name,

-               void *opaque, char **error){

+               void *opaque, const char **error){

     AVEvalExpr * e = ff_parse(s, const_name, func1, func1_name, func2, func2_name, error);

     double d;

     if (!e) return NAN;

@@ -430,7 +430,7 @@ attribute_deprecated double ff_eval(char *s, double *const_value, const char **c

                double (**func1)(void *, double), const char **func1_name,

                double (**func2)(void *, double, double), char **func2_name,

                void *opaque){

-    char *error=NULL;

+    const char *error=NULL;

     double ret;

     ret = ff_eval2(s, const_value, const_name, func1, func1_name, func2, func2_name, opaque, &error);

     if (error)

@@ -55,7 +55,7 @@ double ff_eval(char *s, double *const_value, const char **const_name,

 double ff_eval2(char *s, double *const_value, const char **const_name,

                double (**func1)(void *, double), const char **func1_name,

                double (**func2)(void *, double, double), char **func2_name,

-               void *opaque, char **error);

+               void *opaque, const char **error);

 typedef struct ff_expr_s AVEvalExpr;

@@ -74,7 +74,7 @@ typedef struct ff_expr_s AVEvalExpr;

 AVEvalExpr * ff_parse(char *s, const char **const_name,

                double (**func1)(void *, double), const char **func1_name,

                double (**func2)(void *, double, double), char **func2_name,

-               char **error);

+               const char **error);

 /**

  * Evaluates a previously parsed expression.

  * @param const_value a zero terminated array of values for the identifers from ff_parse const_name