Missing abstraction for working with big numbers about web3swift HOT 7 CLOSED

@Biboran/z please, pay attention to this issue

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However, most of the use cases will be:

1. Arithmetic operators +, -, *, /, %, +=, -=, *=, /=, %=
2. Output (prettifier, string conversion)
3. Working with decimals — we will have large Int and then we need to set precision.
4. Working with hex <-> Int

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@rockfridrich design wise, I would want to stay away from representing numerical types in the library as big numbers because the user of the library working with ethereum is already likely to depend on some big number library. If we can try to stick to String, Data/Array<UInt8> and behavior for objects we should do that. In the case we will have to use a library for arithmetic operations we shouldn't expose these dependencies to the user of the library.

1. Arithmetic operators +, -, *, /, %, +=, -=, *=, /=, %=

Lets list the cases where we might need arithmetic operations on big numbers in the library.

2. Output (prettifier, string conversion)

I believe we should do that through our own numeric type that will be able to return its decimal and hex representation as a string.

3. Working with decimals — we will have large Int and then we need to set precision.

I am not sure what you mean. Could you please elaborate?

4. Working with hex <-> Int

Lets keep it same as 2.

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I gave it a though and I think we should get rid of NumberScalar. Let's model all numbers as 2s complements BytesScalar and make a bunch of objects to validate and operate on those numbers. Let's also make a StringScalar to convert them to string representation decimal.

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@Biboran the first arithmetic and comparison operations I got in mind is checking if the user has enough Ether of tokens to perform the procedure. In the case of ether, we are checking account balance, sending amount and transaction fee. In case the user does not have enough Ether we can throw an error in high domain objects.

For the decimals, we often convert large Ints to decimal numbers based on some power. For example, ETH is 10^18 WEI or gas price is calculated in Gwei (10^9). Another example, the token balance is calculated and displayed as:
{balance}/10^{token decimals}, however when we perform calls and transactions to contract we need to deal with integers.

We need to cover these use cases to simplify everyday operations. Here are some ideas about how to structure number classes.

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Job gh:blockstoreapp/web3swift#60 is not assigned, can't get performer

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The job is not in WBS, won't close the order

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