fixed #5260: return self from floor for values >= 2^52

[arnabnandy7]

Description

This PR fixes a bug in number.floor where finite numbers of magnitude $\ge 2^{63}$ were incorrectly returning saturated values (about $\pm 9.22 \times 10^{18}$) due to narrowing conversion to i64.

Problem

number.floor was computing trunc = ^.as-i64.as-number. The conversion as-i64 is backed by Double.longValue(). For finite doubles whose magnitude is $\ge 2^{63}$, Double.longValue() saturates to Long.MAX_VALUE or Long.MIN_VALUE per Java Language Specification narrowing rules, causing floor of values like 1e20 or -1e20 to return the saturated boundary value.

Solution

Since double-precision floating point numbers have 52 mantissa bits, any double value with a magnitude $\ge 2^{52}$ cannot represent a fractional part and is already an exact mathematical integer.

We update the floor implementation to check if the magnitude is $\ge 2^{52}$ (specifically $\ge 4503599627370496$ or $\le -4503599627370496$), and if so, return the number itself unchanged. This bypasses the narrowing conversion path entirely for values where the result is guaranteed to be equal to the input.

Related Issues

Closes #5260

[github-actions]

🚀 Performance Analysis

All benchmarks are within the acceptable range. No critical degradation detected (threshold is 100%). Please refer to the detailed report for more information.

Click to see the detailed report

Test	Base Score	PR Score	Change	% Change	Unit	Mode
benchmarks.XmirBench.xmirToEO	12628.043	12583.618	-44.425	-0.35%	ms/op	Average Time

✅ Performance gain: benchmarks.XmirBench.xmirToEO is faster by 44.425 ms/op (0.35%)

[0crat]

@arnabnandy7 It is not a good idea to name Git branches the way you named this one: "fix/number-floor-overflow". You've earned -6 points. Next time, better give your branch the same name as the number of the ticket that you are solving. In this case, a perfect name, for example, would be "5265". Your running score is -6; don't forget to check your Zerocracy account too).

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[0crat]

@arnabnandy7 Thanks for the contribution! You've earned +12 points for this: +16 as a basis; -4 for too few (18) hits-of-code. Please, keep them coming. Your running score is +6; don't forget to check your Zerocracy account too).