Module tagged_stack 

Tagged Stack Implementation

A contiguous array of 8-byte tagged values for high-performance stack operations.

Tagged Value Encoding (8 bytes)

- Odd (bit 0 = 1): Int — 63-bit signed integer
    tagged = (value << 1) | 1
    value  = tagged >> 1  (arithmetic shift)

- 0x0: Bool false
- 0x2: Bool true

- Even, > 2: Heap pointer to Box<Value>
    All heap pointers are 8-byte aligned (low 3 bits = 0)
    and always > 2, so no ambiguity with false/true.

Stack Layout

Stack: contiguous array of 8-byte u64 slots
┌──────┬──────┬──────┬──────┬─────┐
│  v0  │  v1  │  v2  │  v3  │ ... │
│(8 B) │(8 B) │(8 B) │(8 B) │     │
└──────┴──────┴──────┴──────┴─────┘
                               ↑ SP

Structs

TaggedStack

Stack state for the tagged value stack

Constants

DEFAULT_STACK_CAPACITY

Default stack capacity (number of stack values)

STACK_VALUE_SIZE

Size of StackValue in bytes (8 bytes = 1 x u64)

TAG_FALSE

Tagged value for Bool false

TAG_TRUE

Tagged value for Bool true

Functions

is_tagged_heap

Check if a tagged value is a heap pointer (not Int, not Bool)

is_tagged_int

Check if a tagged value is an inline integer

seq_stack_base^⚠

Safety

seq_stack_capacity^⚠

Safety

seq_stack_clone^⚠

Safety

seq_stack_free^⚠

Safety

seq_stack_grow^⚠

Safety

seq_stack_new

seq_stack_new_default

seq_stack_set_sp^⚠

Safety

seq_stack_sp^⚠

Safety

tag_int

Encode an i64 as a tagged integer.

untag_int

Decode a tagged integer back to i64 (arithmetic shift)

Type Aliases

StackValue

An 8-byte tagged stack value.