giles
0fb87e3b1c
S-expression parser, evaluator, and primitive registry in shared/sexp/. 109 unit tests covering parsing, evaluation, special forms, lambdas, closures, components (defcomp), and 60+ pure builtins. Test infrastructure: Dockerfile.unit (tier 1, fast) and Dockerfile.integration (tier 2, ffmpeg). Dev watch mode auto-reruns on file changes. Deploy gate blocks push on test failure. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
157 lines
4.6 KiB
Python
157 lines
4.6 KiB
Python
"""
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Core types for the s-expression language.
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Symbol — unquoted identifier (e.g. div, ~card, map)
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Keyword — colon-prefixed key (e.g. :class, :id)
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Lambda — callable closure created by (lambda ...) or (fn ...)
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Nil — singleton null value
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"""
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from __future__ import annotations
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from dataclasses import dataclass, field
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from typing import Any
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# ---------------------------------------------------------------------------
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# Nil
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# ---------------------------------------------------------------------------
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class _Nil:
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"""Singleton nil value — falsy, serialises as 'nil'."""
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_instance: _Nil | None = None
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def __new__(cls):
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if cls._instance is None:
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cls._instance = super().__new__(cls)
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return cls._instance
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def __bool__(self):
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return False
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def __repr__(self):
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return "nil"
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def __eq__(self, other):
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return other is None or isinstance(other, _Nil)
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def __hash__(self):
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return hash(None)
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NIL = _Nil()
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# ---------------------------------------------------------------------------
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# Symbol
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# ---------------------------------------------------------------------------
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@dataclass(frozen=True)
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class Symbol:
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"""An unquoted symbol/identifier."""
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name: str
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def __repr__(self):
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return f"Symbol({self.name!r})"
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def __eq__(self, other):
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if isinstance(other, Symbol):
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return self.name == other.name
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if isinstance(other, str):
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return self.name == other
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return False
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def __hash__(self):
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return hash(self.name)
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@property
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def is_component(self) -> bool:
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"""True if this symbol names a component (~prefix)."""
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return self.name.startswith("~")
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# ---------------------------------------------------------------------------
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# Keyword
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# ---------------------------------------------------------------------------
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@dataclass(frozen=True)
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class Keyword:
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"""A keyword starting with colon (e.g. :class, :id)."""
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name: str
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def __repr__(self):
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return f"Keyword({self.name!r})"
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def __eq__(self, other):
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if isinstance(other, Keyword):
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return self.name == other.name
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return False
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def __hash__(self):
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return hash((":", self.name))
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# ---------------------------------------------------------------------------
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# Lambda
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# ---------------------------------------------------------------------------
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@dataclass
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class Lambda:
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"""A callable closure.
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Created by ``(lambda (x) body)`` or ``(fn (x) body)``.
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Captures the defining environment so free variables resolve correctly.
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"""
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params: list[str]
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body: Any
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closure: dict[str, Any] = field(default_factory=dict)
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name: str | None = None # optional, set by (define name (fn ...))
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def __repr__(self):
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tag = self.name or "lambda"
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return f"<{tag}({', '.join(self.params)})>"
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def __call__(self, *args: Any, evaluator: Any = None, caller_env: dict | None = None) -> Any:
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"""Invoke the lambda. Requires *evaluator* — the evaluate() function."""
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if evaluator is None:
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raise RuntimeError("Lambda requires evaluator to be called")
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if len(args) != len(self.params):
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raise RuntimeError(
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f"{self!r} expects {len(self.params)} args, got {len(args)}"
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)
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local = dict(self.closure)
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if caller_env:
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local.update(caller_env)
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for p, v in zip(self.params, args):
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local[p] = v
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return evaluator(self.body, local)
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# ---------------------------------------------------------------------------
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# Component
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# ---------------------------------------------------------------------------
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@dataclass
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class Component:
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"""A reusable UI component defined via ``(defcomp ~name (&key ...) body)``.
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Components are like lambdas but accept keyword arguments and support
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a ``children`` rest parameter.
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"""
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name: str
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params: list[str] # keyword parameter names (without &key prefix)
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has_children: bool # True if &rest children declared
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body: Any # unevaluated s-expression body
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closure: dict[str, Any] = field(default_factory=dict)
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def __repr__(self):
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return f"<Component ~{self.name}({', '.join(self.params)})>"
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# ---------------------------------------------------------------------------
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# Type alias
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# ---------------------------------------------------------------------------
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# An s-expression value after evaluation
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SExp = int | float | str | bool | Symbol | Keyword | Lambda | Component | list | dict | _Nil | None
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