Expression functions

Expression functions

This page is generated from the test data (EXPRESSION_TABLES and QUANTIFIER_TABLES in @meshfw/runtime/testing); a test fails when it is out of date. It is the written definition of ADR-0012, option A: Mesh defines each function, follows SQL’s three-valued logic where the databases agree, and the in-memory form and every SQL evaluator must give these answers. How the rules are applied is in Expressions.

null is both NULL and an unknown boolean. D(n) is the instant n milliseconds after the epoch. T stands for one class of number, string, boolean, date or enum, the same on both sides.

Anything not listed here (string ordering, truthiness, ==, string concatenation, string methods) is not translated: it stays plain TypeScript with JavaScript’s rules, and the build warns.

a === b (eq)

Signature: (T, T) -> boolean. Null behaviour: any operand null: unknown.

a !== b (ne)

Signature: (T, T) -> boolean. Null behaviour: any operand null: unknown.

a === null (isNull)

Signature: (any) -> boolean. Null behaviour: never unknown.

a !== null (isNotNull)

Signature: (any) -> boolean. Null behaviour: never unknown.

a < b (lt)

Signature: (number | date, same) -> boolean. Null behaviour: any operand null: unknown.

a <= b (lte)

Signature: (number | date, same) -> boolean. Null behaviour: any operand null: unknown.

a > b (gt)

Signature: (number | date, same) -> boolean. Null behaviour: any operand null: unknown.

a >= b (gte)

Signature: (number | date, same) -> boolean. Null behaviour: any operand null: unknown.

a && b (and)

Signature: (boolean, boolean) -> boolean. Null behaviour: Kleene.

a || b (or)

Signature: (boolean, boolean) -> boolean. Null behaviour: Kleene.

!a (not)

Signature: (boolean) -> boolean. Null behaviour: null stays unknown.

a + b (add)

Signature: (number, number) -> number. Null behaviour: any operand null: null.

a - b (sub)

Signature: (number, number) -> number. Null behaviour: any operand null: null.

a * b (mul)

Signature: (number, number) -> number. Null behaviour: any operand null: null.

a / b (a float or decimal operand) (div)

Signature: (number, number) -> number. Null behaviour: exact division; any operand null, or a zero divisor: null.

a / b (both integers) (idiv)

Signature: (integer, integer) -> integer. Null behaviour: truncates toward zero; any operand null, or a zero divisor: null.

-a (neg)

Signature: (number) -> number. Null behaviour: null: null.

a.length (length)

Signature: (string | list) -> number. Null behaviour: null string: null; a list is never null.

now() (now)

Signature: () -> date. Null behaviour: never null; one instant per scope.

today() (today)

Signature: () -> date. Null behaviour: never null; now() at 00:00 UTC.

a ?? b (coalesce)

Signature: (T, T) -> T. Null behaviour: a unless a is null, else b.

c ? a : b (cond)

Signature: (boolean, T, T) -> T. Null behaviour: unknown test: the else branch.

Quantifiers over a loaded has-many

some, every, find and filter take a list and a predicate. The column lists the predicate’s result for each element, in order (T true, F false, N unknown); the elements are numbered from 0. An unknown predicate never makes some true and always makes every false; M10 translates every(p) as NOT EXISTS (… WHERE p IS NOT TRUE). A list that was not loaded throws FrameworkError.

some

every

find

filter