Some math functions return different results between 0.11.0 and 0.12.1

Example: exp(2 * ln(3)) returns 8.999999999999998 in 0.11.0 and 9.000000000000002 in 0.12.1.

To repro:
```
select , exp(2 * ln(3)) from
```
for any table. The result is computed during parsing.

Start by reproducing the SQL query shown in the issue across versions 0.11.0 and 0.12.1, then trace where the result is computed during parsing. Done means identifying the source of the differing floating-point result and adding coverage or a documented correction for the expected behavior.

Written by the indexing model from the issue text.