Look up the element type of a column by name.

Like Lookup, but returns a harmless fallback (Int) instead of TypeError when the column is not found. Use together with AssertPresent so the error fires exactly once.

Check whether a column name exists in a schema (type-level Bool).

Remove a column by name from a schema.

Unwrap a Maybe from a type after we impute values.

Select a subset of columns by a list of names.

Exclude columns by a list of names.

Rename a column in the schema.

Rename multiple columns.

Append two type-level lists.

Add type to the end of a list.

Reverse a type-level list.

Extract column names as a type-level list of Symbols.

Assert that a column name is absent from the schema (for derive/insert).

Assert that a column name is present in the schema.

Assert that a column name is present in the schema.

Assert that each join key has the same element type in both schemas, modulo Maybe-wrapping on either side (the runtime join matches a nullable key column against a plain one). Use together with AssertAllPresent, which reports keys missing from either schema; absent keys are skipped here so the error fires exactly once.

Emit a readable compile error when the column named name is not a real-number type, naming the calling function fn, the column, and the type it actually has. Used by the numeric extractors so a wrong column type reads as a repairable message rather than a bare No instance for Real ….

Constraint that every column in the schema is a real (numeric), unboxed type. Lets the whole-frame matrix extractors (toDoubleMatrix and friends) be total — a non-numeric or nullable column is a compile error (with the offending column named, via AssertRealColumn), not a runtime Left.

Is a a real, unboxed numeric type — i.e. a valid numeric-column element?

Type-level elem for Symbols

Strip Maybe from all columns. Used by filterAllJust.

'("x", (Maybe Double) becomes '("x", Double.)) '("y", Int stays '("y", Int.))

Strip Maybe from a single named column. Used by filterJust.

StripMaybeAt "x" '[ '("x", Maybe Double), '("y", Int)] = '[ '("x", Double), '("y", Int)]

Extract column names that appear in both schemas.

Columns from left whose names do NOT appear in right.

Inner join result schema.

Left join result schema.

Right join result schema.

Full outer join result schema.

Wrap column types in Maybe; idempotent on already-optional columns.

Wrap selected columns in Maybe by name list.

Columns in left whose names collide with right (excluding keys).

Extract Column entries from a schema whose names appear in keys.

Provides runtime evidence of a schema: a list of (name, TypeRep) pairs.

The column names a schema declares, in schema order. Pass it to a reader's options to fetch only those columns:

D.readCsvWithOpts
    D.defaultReadOptions{D.readColumns = Just (schemaColumnNames @(Schema Customer))}
    "customers.csv"

A class that provides a list of Text values for a type-level list of Symbols.