Lesson 26 · Serializing arrays - Build a JSON Parser

Serializing arrays

With scalars and strings writing themselves, arrays are just their elements joined by commas. Today you serialize arrays compactly, recursing into each element.

The goal

Serialize an array value as a compact, comma-separated, bracketed list.

Start here - the target

TO DO

Scenario: Writing arrays as text

Givenan array Value

WhenSerialize is called

Thenan empty array is "[]", an array of Number 1, 2, 3 is "[1,2,3]", and an array of Bool true then Null is "[true,null]"

Andan array whose first element is an array of Number 1 and whose second is Number 2 is "[[1],2]"

Background

An array’s text is the simplest of the containers: an opening bracket, each element serialized in order and separated by a single comma, and a closing bracket. There are no spaces in the compact form - readability is the pretty-printer’s job, two lessons from now. The empty array is just [].

Because Serialize already handles every scalar and string, serializing an array means recursing: call Serialize on each element and join the results. That is the same mutual-recursion shape the parser used, run backward, so nested arrays like [[1],2] serialize correctly with no special handling. Objects work the same way and are next; then a round-trip test will prove parse and serialize are true inverses on canonical input.

Make it work

// array case of Serialize:
//   '[' + join(Serialize(each element), ",") + ']'
// no spaces; recurse into elements so nested arrays fall out for free

CheckpointDONE

Arrays serialize compactly, including nested ones. Commit and stop here.