| """3. Assembler: the extracted values and the reader's choices -> one known value per quantity, in SI. |
| |
| assemble([{"dimension": "speed", "si": 31.3}, {"dimension": "acceleration", "si": 6.9}], |
| {"order": ("u",), "sign": -1, "u0": False, "v0": True, "a_source": None}) |
| -> {"m": 2000.0, "u": 31.3, "a": -6.9, "v": 0.0} |
| |
| Returns None when the values don't fit the choices (e.g. two values for one quantity). |
| """ |
|
|
| DEFAULT_MASS = 2000.0 |
| SYMBOL = {"acceleration": "a", "time": "t", "distance": "s", "mass": "m", "force": "F"} |
|
|
|
|
| def assemble(quantities, choice): |
| speeds = [q["si"] for q in quantities if q["dimension"] == "speed"] |
| others = [(SYMBOL[q["dimension"]], q["si"]) for q in quantities if q["dimension"] != "speed"] |
| if len(speeds) != len(choice["order"]) or len({s for s, _ in others}) < len(others): |
| return None |
| known = {"m": DEFAULT_MASS} | dict(zip(choice["order"], speeds)) | dict(others) |
| for q in ("a", "F"): |
| if q in known: |
| known[q] = choice["sign"] * abs(known[q]) |
| if choice["u0"]: |
| known["u"] = 0.0 |
| if choice["v0"]: |
| known["v"] = 0.0 |
| if choice["a_source"] is not None: |
| known["a"] = choice["sign"] * choice["a_source"] |
| return known |
|
|
