Re: question on variant record

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Matthew Heany said

"The technical term is "discriminant," not "tag field."  And technically, a
"variant record" is a discriminant record only with a variant part (case
statement).  You probably meant "discriminant record" in your subject line."

variant record is a perfectly good term, see for example para 35 of the
introduction to the RM:

35   Record, task, and protected types may have special components called
discriminants which parameterize the type.  Variant record structures that
depend on the values of discriminants can be defined within a record type.


variant_part is a perfectly good syntactic term, so the term variant
record is a perfectly reasonable one, it  means a record with a variant
part.

The other term is discriminaTED record, which is a record type with
discriminants. Note that all variant records have discriminants, but
not all records with discriminants have variant parts, so variant record
is a useful term.

P.S. the term discriminant record is not used in the RM.