Variables & Scope

No declaration keyword

A name is created the same way it’s updated — there’s no let:

x = 5              # untyped
x: Int = 5         # typed — checked the same way function params are

The one assignment rule

name = value (typed or not) updates the nearest existing binding for name in the enclosing scope chain. If none exists anywhere, it creates one in the current (innermost) scope.

counter = 0
i = 0
while i < 3:
    counter = counter + 1   # mutates the OUTER counter -- no special syntax needed
    i = i + 1
print(counter)   # 3

Python needs an explicit global/nonlocal before a nested scope can mutate an enclosing variable — miss it and you get UnboundLocalError. Sense has one rule, no exception to remember:

counter = 0
def add_one():
    counter = counter + 1  # just works
add_one()
print(counter)  # 1

counter = 0
def add_one():
    counter = counter + 1  # UnboundLocalError!
add_one()

`local`: get a genuinely new variable

Want a fresh binding even though an outer one of the same name exists? That’s local:

x = 1
if true:
    local x = 2   # shadows the outer x; does not touch it
    print(x)      # 2
print(x)          # 1 -- outer x is untouched

local always creates in the current (innermost) scope. local name: Type = expr supports a type annotation, same as the untyped form.

Blocks are their own scope

if/while/for bodies, function calls, session bodies, and agent bodies each get their own child scope. A variable first assigned inside one, with no matching name in any enclosing scope, stays local to it:

if true:
    only_inside = 42
print(only_inside)   # error: undefined variable 'only_inside'

`set delegation` and `policy` use the same scope chain

set delegation = <model> (see Model, Ask & Answer) and policy: allow/deny <capability> (see Policy) resolve through this exact mechanism — each scope has its own optional override, found by walking up the parent chain, same as a variable lookup. Nothing new to learn for those.

Continue

Functions

Declaring, calling, closures, and typed parameters.

Control flow

if/else, while, for, break, continue.

Language

AI-Native

Safety

Variables & Scope

No declaration keyword

The one assignment rule

`local`: get a genuinely new variable

Blocks are their own scope

`set delegation` and `policy` use the same scope chain

Continue

Functions

Control flow

​No declaration keyword

​The one assignment rule

​local: get a genuinely new variable

​Blocks are their own scope

​set delegation and policy use the same scope chain

​Continue

Functions

Control flow

No declaration keyword

The one assignment rule

`local`: get a genuinely new variable

Blocks are their own scope

`set delegation` and `policy` use the same scope chain

Continue