/*
  *  call-seq:
  *     prc.curry         => a_proc
  *     prc.curry(arity)  => a_proc
  *
  *  Returns a curried proc. If the optional <i>arity</i> argument is given,
  *  it determines the number of arguments.
  *  A curried proc receives some arguments. If a sufficient number of
  *  arguments are supplied, it passes the supplied arguments to the original
  *  proc and returns the result. Otherwise, returns another curried proc that
  *  takes the rest of arguments.
  *
  *     b = proc {|x, y, z| (x||0) + (y||0) + (z||0) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 6
  *     p b.curry(5)[1][2][3][4][5]  #=> 6
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 6
  *     p b.curry(1)[1]              #=> 1
  *
  *     b = proc {|x, y, z, *w| (x||0) + (y||0) + (z||0) + w.inject(0, &:+) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 10
  *     p b.curry(5)[1][2][3][4][5]  #=> 15
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 15
  *     p b.curry(1)[1]              #=> 1
  *
  *     b = lambda {|x, y, z| (x||0) + (y||0) + (z||0) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> wrong number of arguments (4 or 3)
  *     p b.curry(5)                 #=> wrong number of arguments (5 or 3)
  *     p b.curry(1)                 #=> wrong number of arguments (1 or 3)
  *
  *     b = lambda {|x, y, z, *w| (x||0) + (y||0) + (z||0) + w.inject(0, &:+) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 10
  *     p b.curry(5)[1][2][3][4][5]  #=> 15
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 15
  *     p b.curry(1)                 #=> wrong number of arguments (1 or 3)
  *
  *     b = proc { :foo }
  *     p b.curry[]                  #=> :foo
  */
static VALUE
proc_curry(int argc, VALUE *argv, VALUE self)
{
    int sarity, marity = FIX2INT(proc_arity(self));
    VALUE arity, opt = Qfalse;

    if (marity < 0) {
        marity = -marity - 1;
        opt = Qtrue;
    }

    rb_scan_args(argc, argv, "01", &arity);
    if (NIL_P(arity)) {
        arity = INT2FIX(marity);
    }
    else {
        sarity = FIX2INT(arity);
        if (proc_lambda_p(self) && (sarity < marity || (sarity > marity && !opt))) {
            rb_raise(rb_eArgError, "wrong number of arguments (%d for %d)", sarity, marity);
        }
    }

    return make_curry_proc(self, rb_ary_new(), arity);
}