Conversions
Ask and convert semantic types.
Orientation
Use ? :name to inquire about semantic membership, ~: for a soft conversion, and ~!: for a strict conversion that reports failure.
Ask which semantic type a value satisfies before changing its representation.
A worked example
The final line is the displayed value; the earlier lines set up the experiment. Keep the setup visible so you can tell whether a name, a cell, or a collection is being reused when the expression changes.
Read the result
A conversion does not mutate a binding unless you assign the converted result back.
Try the same question with a fraction and an integer; the distinction matters before choosing a conversion.
Keep going
Continue with Headers and traits for protocol metadata or Physical units for dimensions.