27  Every refusal is the grammar’s

The verbs build a sentence and check nothing. Whether a column exists, whether an aggregation belongs where you put it, whether the types line up: all of that is answered in one place, so both languages get the same answer, in the same words.

R

collect(sales |> keep(reveune > 100))

Error:
! 
illegal: there is no column called `reveune`. Did you mean `revenue`? The table has: region, product, revenue, cost
  |
2 |   then keep where ([reveune] > 100)
  |                     ^^^^^^^

Python

try:
    collect(sales >> keep(col.reveune > 100))
except GodError as refusal:
    print(refusal)

illegal: there is no column called `reveune`. Did you mean `revenue`? The table has: region, product, revenue, cost
  |
2 |   then keep where ([reveune] > 100)
  |                     ^^^^^^^

The whole pipeline is read before any of it runs, so a mistake at step two is reported as a mistake at step two rather than partway through the work.

There is one refusal that cannot work this way, and it is worth knowing which. When widen finds two rows wanting the same cell, that is a fact about the data rather than about the sentence, and the grammar reads column names rather than rows. So that one arrives while the query runs. The words are still the grammar’s, and they still name what to write instead.