hi all. is there any method to make order in an exchange, called from smart contract

same question: is there any on chain solution to make trading order in an exchange/dex ?

yes. but it is very inefficient... i think someone posted smart contract for it in here a while ago

https://github.com/Dylan-Phoon/Ethex/blob/master/Contracts/Ethex.sol

This is modified contract with fees but I haven't properly tested it yet so might not work properly :p

Idex is very good but doesn't use the chain for everything. You wouldn't want to do that or you end up with a terrible performance service like etherdelta