Will I be able to build a decentralised exchange on Cardano CL?
Yes. There’s nothing known for now that would stop you from doing this.
You can also read this whole topic and think of a decentralised exchange as the same kind of functionality but just a lot more complex:
Perhaps this will be very much needed sooner than later given the recent news: Ethereum falls on report second-biggest cryptocurrency is under regulatory scrutiny. https://www.cnbc.com/2018/05/01/ethereum-falls-on-report-second-biggest-cryptocurrency-is-under-regulatory-scrutiny.html
Afaik, Charles was talking about a default DEX being a part of Cardano platform, so might happen in the near future )
I did not know that.
Don’t suppose you have a link - no worries if not.