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The most common positive ions are formed by theĪ neutral atom picks up one or more electrons, a negative ion is produced, Sufficient amount of energy is required to a neutral atom to ionize it.Ĭation may carry +1, +2, +3, etc. Īre those species which have a positive or a negative charge.Īn atom of an element loses one or more electrons, positive ions are formed.
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An atom is composed of two regions: the nucleus, the center of atom contain proton and neutron, and the outer portion of the atom holds electrons in its orbit around the nucleus. However, Electron, Proton and Neutron are regarded as fundamental particles. more than 100 such particles are exist in an atom. Hydrogen, nitrogen and oxygen do not exist independently.Īn atom is further composed of subatomic particles like electron, proton, neutron, hypron, neutrino, anti-neutrino etc. Atom is the entity that take part in a chemical reaction. Please look at the image on website, because some updates are always possible.To Dalton’s theory atom is smallest particle which could not be divided anyįurther. You can operate on many refs safe in transaction. Refs works similar to database transactions. Retry when other thread change the state during run.ĭo not use not idempotent functions and functions with long time Share access to mutable state for every threads. Some shortcut from the article after suggestion:ĭo not change vars after create. I hope it will help people looking answers in that topic. Share state - when use vars, atoms, agents and refs? I wrote article with summary up the difference between them and help choose when use which one. If you have a multi-threaded program and each thread needs its own private state, put that state in a var.Īs far as real-world examples go, if you provide an example of what you are trying to do, we can tell you what to use. Vars are for when you need to store something on a per-thread basis. You can get the value of the agent and tell it to apply a function to its value, but you don't know when the function will run or what value the function will be applied to. As a non-trivial example, if you are trying to cache the return values of a function (ie memoize it), using an atom is probably safe - the state is invisible to everything outside the function, so you don't need to worry about a state change inside the function messing anything up.Īgents primary point is that they run in a different thread. If you will never need to change the state of the atom and anything else at the same time, using at atom is safe (in particular, if there is only one piece of state in the entire program, you can put it in an atom). Any time you have multiple different pieces of state, using refs isn't a bad idea.Ītoms are for independent state that needs to be synchronized between threads. If you need to keep track of a bunch of different things and you will sometimes need to do operations that write to several of the things at once, use refs. Refs are for state that needs to be synchronized between threads. Synchronous access is used when the call is expected to wait until all Identities have settled before continuing.Īsynchronous access is "fire and forget" and let the Identity reach its new state in its own time. Uncoordinated access is used when only one Identity needs to update, this is a very common case. Vars are for thread local isolated identities with a shared default value.Ĭoordinated access is used when two Identities needs to change together, the classic example is moving money from one bank account to another, it needs to either move completely or not at all.Agents are for Uncoordinated asynchronous access to a single Identity.Atoms are for Uncoordinated synchronous access to a single Identity.Refs are for Coordinated Synchronous access to "Many Identities".Start by watching this video on the notion of Identity and/or studying here. I highly recommend "The Joy of Clojure" or "programming Clojure" for a real answer to this question, I can reproduce a short snip-it of the motivations for each: