I try to run the source code of chapter 6 of the book "openframeworks essentials’ but there is a conflict of types I think (I’m a beginner). These are the screenshots.
Can anybody help me out please
The book was written before that OF adopted GLM as the standard library for math operations, most probably it is an error that has to do with this. But if you do not post the error message, it is really difficult to guess 
Which error are you receiving?
sphere.getMesh().getVertices() returns an vector<glm::vec3>. Be sure that the variable vertices0 is defined as such. From your screenshot, it also looks like the sphere is undefined.
I would not recommend you to learn OF from a book that it has been proved to be a bit old and not up-to-date.
These are good resources:
- the ofBook https://openframeworks.cc/ofBook/chapters/foreword.html
- Your examples folder. Almost everything is covered there
- The video tutorial by @lewislepton, https://www.youtube.com/watch?v=IKSTo_0pB28&index=51&list=PL4neAtv21WOmrV8z9rSzL20QpdLU1zJLr
thank you, I already figured out the glm::vec3 notation. Now I’m dealing with a deleted function error …
You do not even need ofxFloatSlider, we have ofParameter<float>, check in examples/gui