calculator

# Calculator Math, units, dates, and currency conversion. ## Math Expressions Safe evaluation via Python: ```python import ast result = eval(compile(ast.parse("2**10 + 3.14 * 2", mode='eval'), '', 'eval')) ``` Complex math: ```python import math math.sqrt(144) # 12.0 math.log2(1024) # 10.0 math.factorial(10) # 3628800 math.pi # 3.14159... ``` ## Unit Conversions | Category | Conversions | |----------|------------| | Temperature | `C↔F: F = C*9/5+32` | | Length | km↔mi (×0.621371), m↔ft (×3.28084), cm↔in (×0.393701) | | Weight | kg↔lb (×2.20462), g↔oz (×0.035274) | | Volume | L↔gal (×0.264172) | | Data | KB↔MB↔GB↔TB (÷1024) | ## Date Calculations ```python from datetime import datetime, timedelta from zoneinfo import ZoneInfo # Days between dates (datetime(2026, 12, 31) - datetime.now()).days # Add/subtract time datetime.now() + timedelta(days=30, hours=2) # Timezone conversion dt = datetime.now(ZoneInfo("Asia/Shanghai")) dt.astimezone(ZoneInfo("America/New_York")) ``` ## Currency Exchange Free API (no key required): ```bash curl -s "https://open.er-api.com/v6/latest/USD" | python3 -c " import sys,json; d=json.load(sys.stdin)['rates'] print(f\"1 USD = {d['CNY']:.4f} CNY\") print(f\"1 USD = {d['EUR']:.4f} EUR\") print(f\"1 USD = {d['JPY']:.2f} JPY\") " ``` ## Common Formulas ```python # BMI bmi = weight_kg / (height_m ** 2) # Compound interest A = P * (1 + r/n) ** (n*t) # Percentage change change = (new - old) / old * 100 ``` ## Script ```bash python3 scripts/calc.py eval "2**32 - 1" python3 scripts/calc.py convert 100 km mi python3 scripts/calc.py date "2026-12-31" days-until python3 scripts/calc.py currency 100 USD CNY ```