Support rational constants

[seanyoung]

In Solidity, rationals are supported as long as they are compile-time constants. e.g. this is supported:

uint x = .5 * 8;

Also, fractions can be written with scientific notation: 1e-2 or 0.001e2.

Fractions can be added/subtracted at compiler time, but fractions cannot be added to integers, like:

uint x = 1;
uint y = x + 0.1;

This change requires:

• Changes to the lexer to support lexing fractions
• Add new type to AST Type::Rational
• Add funtion to evaluate expression of rationals at compile time
• Implicit casting should allow round rationals convert to integers
• Tests for this

[seanyoung]

I've left a review. Looks very good so far. Please let me know if you need any help

[janus]

@seanyoung Please review my code before. I changed coerce_integer to coerce_number

[seanyoung]

• fn coerce_number() should return Type::Rational if either l or r is a rational
• there needs to be a funcion like fn eval_const_number() for rational expressions (something like eval_const_rational)
• fn cast() should check if it can cast from Type::Rational to Type::Uint(n) or Type::Int()
  • it should eval the rational expression using eval_const_rational and see if it is whole number, and not negative for Type::Uint(n)
• in src/codegen/expression.rs fn expression, if a rational expression is found, eval_const_should be called

And then it will be complete. Thanks.

[janus]

* fn coerce_number() should return Type::Rational if either l or r is a rational

* there needs to be a funcion like fn eval_const_number() for rational expressions (something like eval_const_rational)

* fn cast() should check if it can cast from Type::Rational to Type::Uint(n) or Type::Int()

  * it should eval the rational expression using eval_const_rational and see if it is whole number, and not negative for Type::Uint(n)

* in src/codegen/expression.rs fn expression, if a rational expression is found, eval_const_should be called

And then it will be complete. Thanks. Thanks

[janus]

* coerce_number

This is what I have already inside coerce_number function:

        (Type::Rational, Type::Int(_)) => {
            return Ok(Type::Rational);
        }
        (Type::Rational, Type::Uint(_)) => {
            return Ok(Type::Rational);
        }
        (Type::Uint(_), Type::Rational) => {
            return Ok(Type::Rational);
        }
        (Type::Int(_), Type::Rational) => {
            return Ok(Type::Rational);
        }

Is it not complete?

[seanyoung]

I guess so, you also need to check for both l and r being rational.

What I forgot to mention is that you need a simple test case that shows that "uint x = 2.5 + 3.5 - 1;" works

[janus]

@seanyoung I would like to write test for the parser to verify my code, like we have for lexer. Is there something like that?

[seanyoung]

I would suggest adding a test like this one: https://github.com/hyperledger-labs/solang/blob/main/tests/solana_tests/simple.rs#L94-L142

[janus]

@seanyoung I got the below to pass: uint x = .5 * 8; uint x = 1; uint y = x + 0.1;

However, these are failing: 1e-2 0.001e2

I will debug my code. Please go through my code ( and tests) and comment.

This link is broken, https://solang.readthedocs.io/en/latest/installing.html#installing-llvm-on-linux .

[seanyoung]

I've fixed the link. Thank you for mentioning that.

Your code looks good. See my comment on the pull request. You do need to fold the work into one commit, and make sure you have your full name in the Signed-off-by line.

[janus]

@seanyoung I have added your comments to the code. Please review.

NB I have learnt so much and wont mine doing more tasks in the future.

[janus]

@seanyoung I need help. I don't know how to get Visual Code Extension test to pass. I need step by step instruction.

[seanyoung]

Change https://github.com/hyperledger-labs/solang/blob/main/vscode/src/test/suite/extension.test.ts#L35 from:

unrecognised token `}', expected "!", "(", "+", "++", "-", "--", "[", "address", "bool", "bytes", "delete", "false", "function", "mapping", "new", "payable", "string", "this", "true", "~", Bytes, Int, Uint, address, hexnumber, hexstring, identifier, number, string

to

unrecognised token `}', expected "!", "(", "+", "++", "-", "--", "[", "address", "bool", "bytes", "delete", "false", "function", "mapping", "new", "payable", "string", "this", "true", "~", Bytes, Int, Uint, address, hexnumber, hexstring, identifier, number, rational, string

Please also note the review I've left. Should not take long to fix

[janus]

@seanyoung

I get error message if I remove Int/Uint/Value.

test.sol:4:26-28: error: expected ‘uint256’, found rational
Line 4:
    uint x = .5 * 8;
    ---------^^
thread 'solana_tests::simple::returns' panicked at 'called `Option::unwrap()` on a `None` value', src/emit/mod.rs:4348:54

There may be something wrong with my cast then.

[janus]

@seanyoung Thanks so much. Ready for final review.

[seanyoung]

There have been no changes the PR since the last review

[seanyoung]

Please merge all the changes into one commit and push so they are visible at https://github.com/hyperledger-labs/solang/pull/384

[janus]

Please merge all the changes into one commit and push so they are visible at #384

@seanyoung Done.

[seanyoung]

@Web3Foundation the work has been completed, see https://github.com/hyperledger-labs/solang/pull/384

Thanks

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[seanyoung]

@Web3Foundation a reminder, this work has been completed and merged. Thanks