Session
Session — a first-class handle to a REPL session (ADR 0081).
A Session value names a single REPL connection's evaluation state: its
local bindings (the x := 42 layer) and its protocol id. It is not an
Actor — its methods delegate to beamtalk_session_primitives, which reads
the calling process's session context or looks a session up by id.
Session follows the FileHandle / Port representation pattern: a
sealed typed Object subclass with no declared fields, whose per-instance
identity (the session's PID and protocol id) lives in the runtime
representation minted by the factory primitives. Instance methods pass
self to a *For: primitive that extracts that identity.
There is no class-side operation mirror (no Session bindings, no
Session clear) and no globals accessor — globals are workspace
state, reached via Workspace globals. You write Session current bindings
or (Session withId: anId) bindings.
Cross-session access (via withId:) is read-only: reads work against any
live session, but mutating another session's bindings or calling clear
on it raises cross_session_mutation_unsupported.
Examples
Session current bindings keys // => #(#x #y)
Session current bindings at: #x put: 99 // => 99
Session current resolve: #Transcript // => the Transcript singleton
Session current id // => "user-repl-abc-123"
Session current clear // => nil
Methods
Class Methods
The calling process's session as a value. Returns nil outside a
REPL eval context (compiled program code has no session). A later
ADR 0081 phase adds Workspace currentSession as a navigation alias
returning the same value.
Examples
Session current // => Session(repl: _) (in REPL)
Look up a session by its protocol session id. Returns nil if no
such session exists or it is no longer alive. Used for cross-session
access from tooling (LSP, VS Code).
Examples
Session withId: "user-repl-abc-123" // => Session(repl: _) | nil
Instance Methods
Live view of this session's local bindings (the x := 42 layer).
Reads return current values; at:put: and removeKey: mutate
session state (write-through, for the calling session only).
There is no globals here — globals are workspace-owned; use
Workspace globals.
Examples
Session current bindings keys // => #(#x)
Resolve a name exactly the way bare-name lookup does, returning the first match or nil. Order: session locals → workspace globals (bind:as: + singletons) → class registry. Primarily a REPL debugging tool: answers "where does this name resolve from?" interactively.
Examples
Session current resolve: #Transcript // => the Transcript singleton
Clear this session's local bindings. Workspace globals remain.
Examples
Session current clear // => nil
Stable session identifier (matches the protocol session id).
Examples
Session current id // => "user-repl-abc-123"
Originating client surface for this session: "repl", "mcp", "lsp",
"liveview", "ide", "attach", or "unknown". Immutable for the
session's lifetime. Read-only and not liveness-checked — a dead
session still reports where it came from, which is exactly when you want
it for debugging.
Examples
Session current kind // => "repl"
Full origin/debug metadata as a Dictionary: id plus kind and, where
known, peer (remote host:port), node (calling node), user, and
connected_at. The primary "what is this session?" introspection tool.
Examples
Session current info // => #{#id => "...", #kind => "repl", ...}
Developer display: Session(<kind>: <id>), e.g.
Session(repl: session_123_ab). Not liveness-checked, so printing a
list of sessions (Workspace sessions) never raises if one has died.
Examples
Session current printString // => "Session(repl: session_123_ab)"
Inherited Methods
From Object
Return the class of the receiver.
Examples
42 class // => Integer
"hello" class // => String
Test if the receiver is nil. Returns false for all objects except nil.
Examples
42 isNil // => false
nil isNil // => true
Test if the receiver is not nil. Returns true for all objects except nil.
Examples
42 notNil // => true
nil notNil // => false
If the receiver is nil, evaluate nilBlock. Otherwise return self.
Examples
42 ifNil: [0] // => 42
nil ifNil: [0] // => 0
If the receiver is not nil, evaluate notNilBlock with self.
Examples
42 ifNotNil: [:v | v + 1] // => 43
nil ifNotNil: [:v | v + 1] // => nil
If nil, evaluate nilBlock; otherwise evaluate notNilBlock with self.
Examples
42 ifNil: [0] ifNotNil: [:v | v + 1] // => 43
nil ifNil: [0] ifNotNil: [:v | v + 1] // => 0
If not nil, evaluate notNilBlock with self; otherwise evaluate nilBlock.
Examples
42 ifNotNil: [:v | v + 1] ifNil: [0] // => 43
nil ifNotNil: [:v | v + 1] ifNil: [0] // => 0
Return the developer-readable (Debug) string representation.
printString is the Debug protocol (ADR 0094): the self-describing,
structural form used by the REPL, logs, and by any other printString
that nests this object. It is the REPL default — evaluating an expression
shows its printString.
This default returns the bare class name (no a/an article — the
old "a ClassName" form was dropped in ADR 0094). Value overrides it
with the structural ClassName(field: value, ...) form, actors render as
Actor(ClassName, pid), supervisors as Supervisor(ClassName, pid) /
DynamicSupervisor(ClassName, pid), and primitive types (Integer, String,
List, …) override it with their own richer output. Authors rarely override
printString directly — the default is derived.
Examples
42 printString // => "42"
Return the user-facing (Display) string representation.
displayString is the Display protocol (ADR 0094): the human-facing
form. It is the hook the language pulls during string interpolation —
every {...} segment renders via the value's displayString. Developers
rarely call it directly; they override it when a value has a natural
human rendering (e.g. Money → $10.50, where printString would still
show the Debug form).
It defaults to printString, so most types need no override. String
and Symbol demonstrate the split: "hi" printString → "\"hi\""
(quoted, Debug) while "hi" displayString → "hi" (plain, Display);
likewise #foo drops its # prefix under displayString.
displayString is not part of the Printable protocol (deferred per
ADR 0094 §5).
Examples
42 displayString // => "42"
Open a navigable Inspector cursor on the receiver.
ADR 0095 Phase 3 (BT-2504). inspect is repurposed from -> String
(the ADR-0094 deferral) to the verb that produces an Inspector — a
live, immutable cursor for drilling into the object (Inspector on: self).
anObject inspect is the shorthand; Inspector on: anObject is the
explicit spelling. The cursor exposes fields/at:/path/refresh/
printString (an indented text tree) and asDictionaries (the MCP/browser
wire form); see Inspector.
This is a breaking change: code that used inspect for its old
String result must switch to printString (the structural Debug string,
ADR 0094) — a transitional lint flags inspect used directly in ++/
string position.
Examples
42 inspect kind // => #value
(Point x: 3 y: 4) inspect fields size // => 2
(Point x: 3 y: 4) printString // => "Point(x: 3, y: 4)" (the old inspect string)
Return the receiver itself. Useful for cascading side effects.
Examples
42 yourself // => 42
Return a hash value for the receiver.
Examples
42 hash
Test if the receiver responds to the given selector.
Examples
42 respondsTo: #abs // => true
Return the names of fields.
Examples
42 fieldNames // => #()
Return the value of the named field.
Examples
object fieldAt: #name
Set the value of the named field (returns new state).
Examples
object fieldAt: #name put: "Alice"
Send a unary message dynamically.
Examples
42 perform: #abs // => 42
Send a message dynamically with arguments.
Examples
3 perform: #max: withArguments: #(5) // => 5
Raise an error indicating this method must be overridden by a subclass.
Examples
self subclassResponsibility
Raise an error indicating this method has not yet been implemented.
Use this for work-in-progress stubs. Distinct from subclassResponsibility,
which signals an interface contract violation.
Examples
self notImplemented
Send aValue to the current transcript without a trailing newline.
Nil-safe: does nothing when no transcript is set (batch compile, tests).
Examples
42 show: "value: "
Send aValue to the current transcript followed by a newline.
Nil-safe: does nothing when no transcript is set (batch compile, tests).
Examples
42 showCr: "hello world"
Test if the receiver is an instance of aClass or any of its subclasses.
For class-object receivers, follows Smalltalk semantics: self class
is the metaclass, so the check walks the parallel metaclass hierarchy.
The parallel chain is grounded at ProtoObject class superclass == Class
(ADR 0036), so the metaclass tower merges into the instance-side
Class → Behaviour → Object → ProtoObject chain. As a result,
Integer isKindOf: Object and Integer isKindOf: Class both return true.
Examples
42 isKindOf: Integer // => true
42 isKindOf: Object // => true
#foo isKindOf: Symbol // => true
#foo isKindOf: String // => false
Integer isKindOf: Number // => false (metaclass chain, not instance chain)
Integer isKindOf: Number class // => true (Number class is in the parallel chain)
Integer isKindOf: Object // => true (grounded — Object is reachable via the metaclass tower)
Integer isKindOf: Class // => true (Integer class inherits from Class)
Raise an error with the given message.
Examples
self error: "something went wrong"
Delegate message dispatch to the backing Erlang module (ADR 0101, BT-2720).
This method is a sentinel — a plain Object has no backing Erlang module,
so calling delegate raises an Error at runtime. Stateless Objects
declared with native: have their self delegate method bodies rewritten
by the compiler's codegen phase to call the backing module directly, so the
sentinel is never reached on a native: class.
Unlike Actor's delegate (visible only to Actor subclasses), this
Object-base sentinel is visible to every class, so delegate is a
reserved selector on the Object protocol.
Examples
42 delegate // => ERROR: delegate called on a non-native Object
From ProtoObject
Test value equality (Erlang ==).
Examples
42 == 42 // => true
"abc" == "abc" // => true
Test value inequality (negation of ==).
Examples
1 /= 2 // => true
42 /= 42 // => false
Return the class of the receiver.
Examples
42 class // => Integer
"hello" class // => String
Handle messages the receiver does not understand. Override for custom dispatch.
Examples
42 unknownMessage // => ERROR: does_not_understand
Send a message dynamically with an arguments list.
Examples
42 perform: #abs withArguments: #() // => 42
Execute a class method in the caller's process, bypassing gen_server dispatch.
The caller takes responsibility for knowing the method does not mutate class state. Useful for long-running class methods that would otherwise block the class object's gen_server.
Limitations: only resolves methods defined directly on the target class
module (does not walk the superclass chain). Class variables and self
are not available to the method (nil and #{} are passed).
Examples
MyClass performLocally: #run:ctx: withArguments: #(input, ctx)
Send a message dynamically with an arguments list and explicit timeout.
The timeout (in milliseconds or #infinity) applies to the gen_server:call
when the receiver is an actor. For value types, timeout is ignored.
Examples
actor perform: #query withArguments: #(sql) timeout: 30000