Question: I try to create a program that can evaluate simple math expression like "4+4". The expression is given from the user. 

The program saves it in a `char*` and then searches for binary operation (+,-,\*,:) and does the operation. 

The problem is that I can't figure out how to convert the **single** `char` into a `double` value. 

I know there is the `atof` function but I want to convert single `char`.

There is a way to do that without creating a `char*`?

Answer: 
I use that directive in one of my apps and I can get that button to appear by using the using the `file_browser_callback` function in the options. 

Do you get any errors in the JavaScript console? Perhaps you can make a simple CodePen or JS Fiddle of this so people can see your code?

EDIT: Here is a CodePen that does what you want ... it does get that button to appear. The `file_browser_callback` function just logs something to the browser's console but this shows that you can indeed have that button while using that Angular directive.

<http://codepen.io/michaelfromin/pen/BKOGZG>
`{{tinymceOptions}}` in your html may not print the options where the value is a function.

So in your controller include `'uiTinymceConfig'`

Then in your controller function

`uiTinymceConfig.file_browser_callback = function(){
 debugger;
};`

angular-ui-tinymce merges 'tinymceOptions' (expression) and 'uiTinymceConfig' :

```
angular.extend(options, uiTinymceConfig, expression, setupOptions);

```