Struct csx64::asm::expr::SymbolTable

pub struct SymbolTable<T> { /* fields omitted */ }

An appendonly map-like collection of defined symbols.

Importantly, an instance of this type is used during assembly/linking to facilitate pre- and user-defined symbols.

The type T is a tag type that is associated with the value to give it additional context. For instance, the assembler uses tags to keep track of declaration line numbers.

Example

let mut symbols: SymbolTable<usize> = Default::default();
symbols.define("foo".into(), 2u64.into(), 0).unwrap();

Note that in the above example expr was technically modified despite eval() being an immutable method. This is what will be referred to as auto-reducing logic: the value of expr isn’t actually different, it’s just a simpler representation of the same value. From a rust perspective, this is perfectly safe because, aside from using debug formatting, it would be impossible to know anything had happened at all due to the fact that SymbolTable is appendonly and Expr is opaque.

The way this is done is that any sub-expression in the expression tree which successfully evaluates is replaced with a value node with equivalent content. Because of this, if an Expr is evaluated using a given symbol table, it should typically never be evaluated with any other symbol table, lest the final value be potentially corrupted. Best practice has that there should be only one symbol table, which is what the assembly and linking functions included in this crate do implicitly.

Implementations

impl<T> SymbolTable<T>

pub fn new() -> Self

Constructs an empty symbol table.

pub fn define(
    &mut self,
    symbol: String,
    value: Expr,
    tag: T
) -> Result<(), String>

Introduces a new symbol. If not already defined, defines it and returns Ok(()). Otherwise, returns Err(symbol).

pub fn get(&self, symbol: &str) -> Option<&(Expr, T)>

Gets the value of the given symbol if defined.

pub fn clear(&mut self)

Undefines all symbols, effectively restoring the newly-constructed state. This is meant to support resource reuse, and should not be used to remove or modify defined symbols.

pub fn iter(
    &self
) -> impl Iterator<Item = (&String, &(Expr, T))> + FusedIterator

Iterates over the defined symbols and their values, along with the tag.

Trait Implementations

impl<T> BinaryRead for SymbolTable<T> where
    T: BinaryRead, 

fn bin_read<F: Read>(f: &mut F) -> Result<Self>

impl<T> BinaryWrite for SymbolTable<T> where
    T: BinaryWrite, 

fn bin_write<F: Write>(&self, f: &mut F) -> Result<()>

impl<T: Clone> Clone for SymbolTable<T>

fn clone(&self) -> SymbolTable<T>

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T> Debug for SymbolTable<T> where
    T: Debug, 

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Default> Default for SymbolTable<T>

fn default() -> SymbolTable<T>

Returns the “default value” for a type.

impl From<SymbolTable<()>> for Predefines

fn from(symbols: SymbolTable<()>) -> Predefines

Constructs a new set of predefines from a symbol table.

impl<T> SymbolTableCore for SymbolTable<T>

fn is_empty(&self) -> bool

Checks if the symbol table is empty.

fn len(&self) -> usize

Gets the number of defined symbols.

fn is_defined(&self, symbol: &str) -> bool

Checks if a symbol with the given name has already been defined.

fn get_expr(&self, symbol: &str) -> Option<&Expr>

Gets the associated expression if defined