overload-operators-dsl
When to Use
- •Mathematical DSL
- •Query builders
- •Expression builders
- •Matrix operations
- •Custom numeric types
- •Making code look like domain notation
When NOT to Use
- •Would be confusing to readers
- •Standard operators have meaning already
- •Single-use code
The Pattern
Implement __add__, __mul__, etc. to make operators build structure.
python
class Vector:
def __init__(self, *components):
self.components = components
def __add__(self, other):
return Vector(*(a + b for a, b in zip(self.components, other.components)))
def __mul__(self, scalar):
return Vector(*(c * scalar for c in self.components))
def __rmul__(self, scalar):
return self * scalar # Handle 2 * v
v = Vector(1, 2, 3)
w = Vector(4, 5, 6)
result = 2 * v + w # Vector math with natural syntax
Example (from pytudes Differentiation.ipynb)
python
class Expression:
"""DSL for symbolic math."""
def __init__(self, op, *args):
self.op, self.args = op, args
# Arithmetic operators build expressions
def __add__(self, other): return Expression('+', self, other)
def __radd__(self, other): return Expression('+', other, self)
def __sub__(self, other): return Expression('-', self, other)
def __rsub__(self, other): return Expression('-', other, self)
def __mul__(self, other): return Expression('*', self, other)
def __rmul__(self, other): return Expression('*', other, self)
def __truediv__(self, other): return Expression('/', self, other)
def __pow__(self, other): return Expression('**', self, other)
def __neg__(self): return Expression('-', self)
# Equality and hashing for use in dicts
def __eq__(self, other):
return (isinstance(other, Expression) and
self.op == other.op and self.args == other.args)
def __hash__(self):
return hash((self.op, self.args))
# Create symbols
x, y, z = Expression('x'), Expression('y'), Expression('z')
# Natural mathematical syntax
polynomial = 3*x**2 + 2*x + 1
derivative = D(polynomial, x) # 6*x + 2
# Simplification table uses expressions as keys
simp_table = {
sin(0): 0,
cos(0): 1,
ln(1): 0,
}
Key Principles
- •Implement
__r*__methods: Handle2 + xnot justx + 2 - •Return new instances: Operators build structure, don't mutate
- •Implement
__eq__and__hash__: For use in sets/dicts - •Readable
__repr__: Show expression structure clearly - •Match domain notation: Math DSL looks like math