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 found a solution my own with several research, trial and error its working fine for me in angular9. following are the steps I followed

1 : Install & import ngx-tinymce refer <https://www.npmjs.com/package/ngx-tinymce>.  

2 : Following is the html snipet where [config]="textEditorConfig" you will point to the configurations of tinymce editor.

```html
<div class="col-sm-12 col-md-12 col-lg-12">
    <label class="label modal-label text-uppercase">Texts</label>
        <tinymce
          *ngIf="viewMode?.key !== 'view'"
          #reportEditor
          formControlName="expectation"
          [config]="textEditorConfig"
        ></tinymce>
        <!--  View Mode -->
        <div class="template-view"
            *ngIf="viewMode?.key == 'view'"
             [innerHtml]="activityDetailForm?.value?.expectation">
         </div> 
 </div>

```

3 : Define tinymce configuration as follows

```
public static htmlEditorConfig =  {
    height: 350,
    theme: 'modern',
    plugins: 'preview fullpage searchreplace directionality visualchars fullscreen  hr pagebreak nonbreaking anchor advlist lists textcolor wordcount contextmenu colorpicker textpattern link image media paste contextmenu',
    toolbar: 'formatselect | bold italic strikethrough forecolor backcolor | link autolink openlink unlink | alignleft aligncenter alignright alignjustify  | numlist bullist outdent indent | image media',
    contextmenu: 'paste link image',
    image_advtab: false,
    image_uploadtab: true,
    a11y_advanced_options: true,
    content_css: [
      '//fonts.googleapis.com/css?family=Raleway&display=swap',
      '//www.tinymce.com/css/codepen.min.css'
    ],

    file_picker_types: 'image',
    file_picker_callback: function (cb) {
    var input = document.createElement('input');
    input.setAttribute('type', 'file');
    input.setAttribute('accept', 'image/*');
    input.onchange = function (e?: HTMLInputEvent) {
      var file = e.target.files[0];

      var reader = new FileReader();
      reader.onload = function (event) {
        console.log("tinymce",event)
        var blobCache =  event.target.result;
        var blobInfo = blobCache;
        cb(blobInfo, { title: file.name });
      };
      reader.readAsDataURL(file);
    };

    input.click();
    interface HTMLInputEvent extends Event {
      target: HTMLInputElement & EventTarget;
    }
  },
  };

```
`{{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);

```