Tables with dictionary rows

[hollasch]

The table structure provides a way to ensure consistent data features, along with a way to default missing values. Given this, it would be useful to have tables with dictionary rows, for cases where it's useful to specify sparse information using the standard defaulting mechanism of tables. This offers several benefits over an array of objects:

1. Explicit field names increases readability, and can be order independent.
2. Fields can have default types and values.
3. Fields (with optional type information) can be required.
4. Unrecognized fields can be reported as errors.

For example:

[#
    a=true, b=1.0, c="foo", d=none, e=normal, f=100%, g=[[1 0][0 1]]
    :
    { b:22.3, d:all }
    { g:rotate(30), f:50%, c:"bar" }
    { a:false, e:heavy }
#]

The result is a data table with three rows, where each row has all values defined, either explicitly or via defaults.

In addition to the above advantages, tables can catch errors based on violations of the schema declaration:

[#
    a=(boolean:), b, c="foo", d=none, e=normal, f=100%, g=[[1 0][0 1]]
    :
    { a:null ... }
    //  ^ Error: type mismatch (detected in clients that care)

    { b:3.7 }
    //      ^ Error: required feature 'a' not defined (it has no default)

    { a:true, b:4.6, x:red }
    //               ^ Error: unrecognized feature 'x'
#]