math_spec.dimensions

Static dim-set checking — a type system whose type is a set of dim names.

Every node's dim set is computable before any data is bound, so this pass runs at load on the resolved AST. The per-node rules are the "Dim algebra" table in docs/reference/language/expressions.md; a constraint's two sides together must equal its dims, and a where or a bound may not exceed the frame.

check_schema(schema, resolved)

Check every declaration's dim rules, on the trees resolved holds for schema.

RAISES	DESCRIPTION
DimensionError	On the first declaration that breaks one.

Source code in src/math_spec/dimensions.py

def check_schema(schema: Spec, resolved: Resolved) -> None:
    """Check every declaration's dim rules, on the trees *resolved* holds for *schema*.

    Raises:
        DimensionError: On the first declaration that breaks one.
    """
    for vname, vdef in schema.variables.items():
        frame = frozenset(vdef.dims)
        context = f"Variable '{vname}'"
        _check_where_dims(resolved.variables[vname], frame, context)
        for side in ('lower', 'upper'):
            bound = getattr(vdef.bounds, side)
            if isinstance(bound, str):
                bdims = frozenset(schema.parameters[bound].dims)
                if not bdims <= frame:
                    raise DimensionError(
                        f"{context}: bounds.{side} parameter '{bound}' has dims "
                        f"{sorted(bdims - frame)} outside the variable's dims "
                        f'{sorted(frame)}.'
                    )

    for ename, node in resolved.expressions.items():
        if not isinstance(node, CasesNode):
            continue
        frame = frozenset(schema.expressions[ename].dims or [])
        for arm in node.arms:
            context = case_context(ename, None if arm.when is None else arm.label)
            if arm.when is not None:
                _check_where_dims(Mask(arm.when), frame, context)
            _check_value_dims(arm.value, schema, frame, context)

    for cname, (expression, where) in resolved.constraints.items():
        frame = frozenset(schema.constraints[cname].dims)
        context = f"Constraint '{cname}'"
        _check_where_dims(where, frame, context)
        got = dims_of(expression, schema, context)
        if got != frame:
            stray, missing = sorted(got - frame), sorted(frame - got)
            detail = (
                f'carries dims {stray} that are not in its dims: {sorted(frame)} — every '
                f'stray dim multiplies the rows this constraint builds; add it to '
                f'dims: if that is intended, or sum it out'
                if stray
                else f'does not carry {missing}, which its dims: declares — the same row '
                f'would be repeated across {missing}; drop it from dims:, or use it '
                f'in the expression'
            )
            raise DimensionError(f'{context}: the expression {detail}.')

    if resolved.objective is not None:
        context = 'The objective'
        got = dims_of(resolved.objective, schema, context)
        if got:
            raise DimensionError(
                f'{context}: the expression carries dims {sorted(got)}, and an objective is one '
                f'number. Wrap each additive term in its own sum(): '
                f'`sum(p * cost) + sum(p_nom * capex)`.'
            )

dims_of(node, schema, context)

The dim set of a resolved expression, checking every rule on the way.

RAISES	DESCRIPTION
DimensionError	On the first rule broken.

Source code in src/math_spec/dimensions.py

def dims_of(
    node: ParsedNode,
    schema: Spec,
    context: str,
) -> frozenset[str]:
    """The dim set of a resolved expression, checking every rule on the way.

    Raises:
        DimensionError: On the first rule broken.
    """
    if isinstance(node, ComparisonNode):
        return _dims(node.left, schema, context) | _dims(node.right, schema, context)
    return _dims(node, schema, context)