Module cel 

VAPP-191 (eApps Q2): expressions, the Rust twin of packages/exponential-ui/src/cel.ts (line by line; read its header for the language). A SUBSET of CEL with ONE number type (a double, like JSON), hand-written so both twins replay fixtures/expressions.json exactly: numbers, dates and error texts. No loops, no user functions, a length cap, no nested comprehensions and a step limit, so it always terminates. The functions are ONE table shared with the A2UI function form ({"call": "mul", …}, call_expression_function); dates run in the team zone (an offset per instant, ExpressionEnv::offset).

Structs

ExpressionEnv

The clock, the team zone and the step limit an evaluation runs with.

Enums

FunctionEffect

VAPP-194 (E1): what calling a function does. Expressions are PURE: a binding, visible, a computed field or a query param never writes. A write changes records or the surface data, a host function reaches outside the surface (a toast, an MCP call, a link, another action); both run only as steps of a package action (crate::host::actions).

Node

A parsed expression (at = the code point it starts at).

Constants

CALENDAR_UNITS

CALL_NAMES

The A2UI form’s names in the bind table (size = the existing len; expr = the string form, {expr, vars}).

DATE_UNITS

Every unit dateAdd / dateDiff take; startOf / endOf take the calendar ones.

DURATION_FORMATS

The formats formatDuration writes.

FUNCTION_NAMES

THE function table (spec §4.2), positional for CEL, named (args) for the A2UI form. Generic only: no working days, no holidays.

HOST_FUNCTIONS

The built-in host functions; every name under a host prefix is one too.

HOST_FUNCTION_PREFIXES

MAX_DEPTH

MAX_LENGTH

The cost caps (spec §4.2): characters (code points), nesting, steps.

MAX_STEPS

WRITE_FUNCTIONS

The functions that write (records, the surface data model).

Functions

call_expression_function

The A2UI function form {call: name, args} with its arguments resolved. Outer None = not an expression function; inner None = no value (an error, like every bind-time function). VAPP-195: a failed call shows its default (absent = no value).

check_expression

Type-check an expression against the names it may read (a kind’s fields, a binding’s value): the type, or the error (the parse error, or the first type error). Types are spelled as JSON ("number", [T], a row object, {"?": T} for a value that may be missing).

effect_words

Why an effectful function is refused in a pure place.

evaluate_counted

VAPP-194: evaluate a parsed tree and count its steps (an action spends one budget over all of its expressions): the result and the steps used.

evaluate_expression

Evaluate an expression over vars: the value, or the error (a syntax, type, range or cost error).

evaluate_node

Evaluate a parsed tree (see parse_expression).

expression_names

VAPP-214: the free names an expression reads, sorted (a macro’s own variable is not free inside its body).

format_timestamp

An instant as YYYY-MM-DDTHH:MM:SS.sssZ (JS toISOString), years 0..9999.

function_effect

The effect of a function by name: the signature table’s (every expression function, every bind-time function) is pure.

is_optional

VAPP-195 (E2): a value that may be missing is T?, spelled {"?": T} (a row never has a field named ?).

optional_type

T? (null and an optional stay as they are).

parse_expression

Parse once (at package validation, or before evaluating): the tree, or the first syntax / cost error (at <code point>: <reason>).

parse_timestamp

An ISO instant (YYYY-MM-DDTHH:MM[:SS[.fff]][Z|±HH:MM], no offset = UTC) as epoch ms; None when it is not one.

path_text

VAPP-195: a value’s path as written (a.b[0].c, m['k']): names, fields and literal indexes; None for anything else.

required_type

T of a T?.

type_display

The name a type prints as in an error: a list list, a row map, an optional T?.

type_name

The runtime type name errors print.