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Null & library enums

Built-in null, optional-value helpers, and enum tables without new syntax—enums are ordinary hashes of name → number. See also Data types and someProgrammingLanguage/SCOPING.md.

1. null

The global null is the single absent value (Python None). Many stdlib calls return null on invalid input.

• type.isNull(x) → 1 or 0.
• test.isNull(x) — same result, for use next to other test.* helpers.
• null.coalesce(a, b) — returns a if a is not null, else b.

2. Control flow vs logic operators

test.ifTrue(cond) and test.while(cond) run the body only when cond == 1. So null does not take the branch (same as 0).

Logical and / or / not treat null as falsy (like 0), so you can write not / short-circuit style conditions without null accidentally behaving as “true.”

3. Library enums

There is no separate enum type yet: an enum is a hash mapping string names to integers (or other ordinals). Register and bind a name with:

enum.createEnum({ "A": 0, "B": 1 }, Color);

Second argument must be an identifier (variable name), like hash.createHashTable.

• enum.name(enumHash, value) — reverse lookup: label for a numeric value (uses hash.getKey internally). Returns null if no matching value.
• enum.equals(a, b) — 1 if both ordinals are equal (numeric equality; both null counts as equal).

4. Example

Repository: examples/features_null_enum.spl (expected output documented in-file).

print.boolean(test.isNull(null));
print.number(null.coalesce(null, 42));
enum.createEnum({ "A": 0, "B": 1 }, Color);
print.string(enum.name(Color, 1));

Reference table filters: null, enum, test (test.isNull), type (type.isNull).