What's the low-level cost to determine whether a given string is "numerical" or not? Also, would "001" be considered a numerical string?
This reminds me of Excel-like programs that by default, automatically detect (and convert) fields that appear to be dates/strings...often to catastrophic effect.
You just hit upon by far my least favorite bug in Excel. Any integers around I think 40000, which are quite easy to come upon in various datasets, are automatically "detected" as a date. It makes Excel very dangerous for reading CSV files.
This reminds me of Excel-like programs that by default, automatically detect (and convert) fields that appear to be dates/strings...often to catastrophic effect.