Implement Number IsInt, IsUint, IsFloat, IsNan

[gavv]

Implement new Number assertions:

• IsInt - succeeds if number is signed or unsigned integer (does not have fractional part)
• IsUint - succeeds if number is unsigned integer (does not have fractional part and is >= 0)
• IsFloat - succeeds if number is not integer (have fractional part, is opposite to IsInt)
• IsNan - succeeds if number is NaN

Each of them, except IsNan, should have optional argument bits which defines maximum allowed bitness for the number, e.g. IsInt(32) means that the number should fit in 32-bit signed integer. See String.AsNumber for en example of optional argument.

For every assertion, also add negative version (NotInt, NotUint, etc).

Each assertion should have documentation comment with example and be covered by unit tests. Don't forget to cover corner cases like NaN, inf, etc.

[deepto98]

I'd like to give this a shot. Can I pick this up?

[gavv]

Sure, thanks!

[gavv]

@deepto98 Hi, do you still have plans on this?

[gavv]

Unassigning, so that someone could pick this up.

[fahimbagar]

@gavv, before I continue, could you check the WIP PR and see whether the solution is fine?

I haven't finished IsFloat and IsNaN, need to clarify something

1. The current solution for integer is to convert them to string first and then use ParseInt. Is this correct?
   • I am wondering why the bit is too flexible. I mean something like this could easily check whether it's integer math.Mod(floatValue, 1.0) == 0. Or maybe limit it to 32 and 64. Wdyt?
2. strconv.ParseFloat recognizes NaN and Inf. Should it be failed on IsFloat case?

ParseFloat recognizes the string "NaN", and the (possibly signed) strings "Inf" and "Infinity" as their respective special floating point values. It ignores cases when matching.
https://pkg.go.dev/strconv#ParseFloat

[gavv]

@fahimbagar thanks for taking up this. Will reply shortly.

[gavv]

Hi, here are some thoughts.

1. Using fmt.Sprintf is an interesting idea, and probably is correct, but instead I'd suggest to use math.Modf and check that the value belongs to desired range (e.g. [0; 2^bits]). Rationale:

   • Are we sure that Sprintf + ParseInt wont loose precision? Are we sure that it wont change in future? Even if it doesn't lose precision currently, why bother, if can just use Modf.

   • There is a task in progress (Migrate Number from float64 to big.Float #191) that switches Number from float64 to big.Float. The approach with Modf will be easier to port to big.Float.

2. I think there is no need to limit bit width to 32/64. Yes, other values are rarely needed, but I see no problem with accepting them. Maybe someone will need to check that integers are in 24 bit range, who knows.

3. Yes, I think NaN and Inf should be accepted by IsFloat. They are correct float values, same as signed zero for example.

[fahimbagar]

Noted, thanks for the advice, @gavv. I'll adjust the PR then.

[fahimbagar]

Hey @gavv, I'm stuck with bitness size in IsFloat & NotFloat. 😅
How to measure the maximum bitness of float other than 32-bit and 64-bit? I don't have quite any experience in this.

Maybe I should wait for #191. Otherwise, this PR can be reviewed.

[gavv]

I think for floats it's ok to limit allowed values to 32 and 64, at least for now. After implementing big.Float we can revise it.

No need to wait for #191, I guess it will take time until it's ready.

[gavv]

Landed!