2.1.1.1.1.3. racketinterpreter.classes.stack¶

class ARType(value)¶

Bases: enum.Enum

The type of an activation record.

PROCEDURE = 'PROCEDURE'¶

PROGRAM = ('PROGRAM',)¶

class ActivationRecord(name: str, type: racketinterpreter.classes.stack.ARType, nesting_level: int)¶

Bases: object

A record in the stack.

An activation record is created for subroutines. It is especially useful whenever there is a need to assign values to names temporarily, e.g. assigning actual parameters to formal parameters when calling a procedure, or initializing builtin procedures to the global scope.

Variables

name (str) – The name of the record, either the procedure name or ‘global’ for the global scope.
type (ARType) – The type of activation record.
nesting_level (int) – The number of activation records below this one.
members (dict) – A mapping of names to values in the record.

__setitem__(name: str, value: Data) → None¶

Define a name within this record.

Parameters

name (str) – The name to be defined.
value (Data) – The value of the name.

__getitem__(name: str) → Data¶

Retrieve the value assigned to a name within this record.

Parameters: name (str) – The name whose value to return.
Returns: The value assigned to the name.
Return type: Data
Raises: KeyError – If there is no value assigned to the name.

get(key) → tp.Optional[Data]¶

static log_stack(msg: str) → None¶

Log messages related to the stack.

If the global constant SHOULD_LOG_STACK is set to True, this method will print out the message.

Parameters: msg (str) – The message to be displayed.

class CallStack¶

Bases: object

A call stack.

A stack data structure that keeps track of a list of activation records. Each activation record represents a subroutine. The stack indicates which subroutine will get control after the current one is finished running.

get(name: str) → Data¶

Retrieves the value assigned to the name.

The activation records are checked starting with the last one. Once an activation is found that contains a value assigned to the name, that value is returned.

Parameters: name (str) – The name to lookup.
Returns: The value assigned to the name.
Return type: Data
Raises: IllegalStateError – If there is no activation record with a value assigned to the name.

peek(levels: int = 1) → racketinterpreter.classes.stack.ActivationRecord ¶

Look at an activation record at the top of the stack without removing it.

Parameters: levels (int) – The ith activation record from the top.
Returns: An activation record counting from the top of the stack.
Return type: ActivationRecord

pop() → racketinterpreter.classes.stack.ActivationRecord ¶

Removes an activation record from the stack.

Returns: An activation record from the top of the stack.
Return type: ActivationRecord

push(ar: racketinterpreter.classes.stack.ActivationRecord) → None¶

Push an activation record onto the stack.

Parameters: ar – An activation record.