Name:

_x_ universal name for the mathematical free variable.

Library names:

sollya_obj_t sollya_lib_free_variable() sollya_obj_t sollya_lib_build_function_free_variable() #define SOLLYA_X_ (sollya_lib_build_function_free_variable())

Description:

Example 1:

   > verbosity=1!;
   > sin(a);
   sin(a)
   > b;
   Warning: the identifier "b" is neither assigned to, nor bound to a library function nor external procedure, nor equal to the current free variable.
   Will interpret "b" as "a".
   a
   > _x_;
   a

Example 2:

   > verbosity=1!;
   > sin(y);
   sin(y)
   > f = proc(a) {
       return sin(a + _x_);
     };
   > rename(y,z);
   Information: the free variable has been renamed from "y" to "z".
   > f(1);
   sin(1 + z)

Example 3:

   > f = sin(y);
   > match f with
       sin(a) : { print("sin of a with a =", a);
                  match a with
                    _x_ : { print("a turns out to be the free variable"); }
            default : { print("a is some expression"); };
                }
       _x_ : { print("Free variable") ; }
       default: { print("Something else"); };
   sin of a with a = y
   a turns out to be the free variable
See also: rename, isbound, proc
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