Equations and transforms API¶

Import equation and transform from bilt. See Equations and Transforms for introductions.

Equations¶

from bilt import equation


@equation
def motion(distance: float, speed: float, duration: float) -> bool:
    return distance == speed * duration

The decorator calls the function with symbolic parameters and requires one relation, normally lhs == rhs. The bool return annotation is conventional; the returned symbolic relation is what Bilt checks.

Use named parameters; positional-only parameters, *args and **kwargs are refused. Symbolic conditions cannot control Python if, and or or.

Rearrangement currently handles addition, multiplication, negation and reciprocals. Powers can appear in forward calculations, but Bilt does not generally invert powers, reductions or selections. For single-equation isolation, the requested variable must occur once in the simplified relation. The default causalization analyser can instead collect repeated unknowns inside supported coupled linear equalities and solve those blocks together. This is not a general nonlinear solver.

Transforms¶

from bilt import transform


@transform
def kinetic_energy(mass: float, speed: float) -> float:
    return 0.5 * mass * speed**2

Bilt uses this only to calculate kinetic_energy from mass and speed. Use explicit named input parameters. Transform source must be inspectable: define transforms in source files. Runtime code is compiled from that source; ordinary globals and closure state are not automatically copied into it. Python-only dependencies can be imported inside a transform body.

The selected backend determines which Python operations can run. Named tensor reductions have a restricted return-expression form; see Tensors. Calling a decorated equation or transform directly invokes its original Python function, not Bilt planning or backend execution.

Declarations and units¶

Annotations are read when decorators run. Import or define their names at runtime, outside if TYPE_CHECKING:. Every occurrence of a shared port must agree on its physical dimension, metadata tags and absolute/relative kind.

Equations check dimensional consistency of their symbolic expressions. Transforms check declarations and supported unit operations, rather than proving arbitrary Python arithmetic correct. See Units API.

Errors¶

Import exceptions from bilt.errors.