csv.py's -L/--list-computed was returning some confusing types:
$ ./scripts/csv.py /dev/null -fa='float(1)' -L
a int sum
^-- huh!?
Turns out csv.py's fold typechecking was all broken. Folds can change
the type, but only at the invocation:
$ ./scripts/csv.py /dev/null -fa='sum(float(1))' -L
a int sum
$ ./scripts/csv.py /dev/null -fa='avg(int(1))' -L
a float avg
$ ./scripts/csv.py /dev/null -fa='int(avg(1))' -L
a float avg
This is maybe defensible for explicit folds, since their evaluation is
also lifted, but not so much for things like literals/fields/etc.
---
Fixed by allowing None to indicate a generic fold, and allowing types to
be lazily figured out in csv.compile.
Christopher Haster
9a224a1c52