expression def in figure 3

[pnwamk]

https://github.com/jsiek/B629-denotational/blob/c2cec309126f700140413fbff5dc6332066ef1a6/notes.tex#L381

TL;DR I think the definition for expressions in figure 3 is wrong... specifically the ... implying we are extending something doesn't make sense to me.

Long: In figure 3 it seems we are defining expressions by extending a previous definition and adding variables (that's how I read the ...).

The previous definition for expressions (in section 1) included binary numerals whose metavariable is b, and in figure 3 we're also given the metavariable b to mean conditions (which are defined in figure 3).

So... I'm just trying to figure out if we still have binary numerals... but they (or conditions) need a different metavariable? or are we not extending the previous expressions we had?

[pnwamk]

I guess as well from our lecture today I had assumed we did not have binary numerals, but had Nats and expressions over Nats instead of binary numeral expressions, etc