Struct AST

pub struct AST { /* private fields */ }

Expand description

Compiled AST (abstract syntax tree) of a Rhai script.

§Thread Safety

Currently, AST is neither Send nor Sync. Turn on the sync feature to make it Send + Sync.

Implementations§

§

impl AST

pub fn empty() -> AST

Create an empty AST.

pub fn source(&self) -> Option<&str>

Get the source, if any.

pub fn set_source(&mut self, source: impl Into<ImmutableString>) -> &mut AST

Set the source.

pub fn clear_source(&mut self) -> &mut AST

Clear the source.

pub fn clone_statements_only(&self) -> AST

Clone the AST’s script statements into a new AST. No functions are cloned.

pub fn merge(&self, other: &AST) -> AST

Merge two AST into one. Both AST’s are untouched and a new, merged, version is returned.

Statements in the second AST are simply appended to the end of the first without any processing. Thus, the return value of the first AST (if using expression-statement syntax) is buried. Of course, if the first AST uses a return statement at the end, then the second AST will essentially be dead code.

All script-defined functions in the second AST overwrite similarly-named functions in the first AST with the same number of parameters.

§Example

use rhai::Engine;

let engine = Engine::new();

let ast1 = engine.compile("
    fn foo(x) { 42 + x }
    foo(1)
")?;

let ast2 = engine.compile(r#"
    fn foo(n) { `hello${n}` }
    foo("!")
"#)?;

let ast = ast1.merge(&ast2);    // Merge 'ast2' into 'ast1'

// Notice that using the '+' operator also works:
// let ast = &ast1 + &ast2;

// 'ast' is essentially:
//
//    fn foo(n) { `hello${n}` } // <- definition of first 'foo' is overwritten
//    foo(1)                    // <- notice this will be "hello1" instead of 43,
//                              //    but it is no longer the return value
//    foo("!")                  // returns "hello!"

// Evaluate it
assert_eq!(engine.eval_ast::<String>(&ast)?, "hello!");

pub fn combine(&mut self, other: AST) -> &mut AST

Combine one AST with another. The second AST is consumed.

Statements in the second AST are simply appended to the end of the first without any processing. Thus, the return value of the first AST (if using expression-statement syntax) is buried. Of course, if the first AST uses a return statement at the end, then the second AST will essentially be dead code.

All script-defined functions in the second AST overwrite similarly-named functions in the first AST with the same number of parameters.

§Example

use rhai::Engine;

let engine = Engine::new();

let mut ast1 = engine.compile("
    fn foo(x) { 42 + x }
    foo(1)
")?;

let ast2 = engine.compile(r#"
    fn foo(n) { `hello${n}` }
    foo("!")
"#)?;

ast1.combine(ast2);    // Combine 'ast2' into 'ast1'

// Notice that using the '+=' operator also works:
// ast1 += ast2;

// 'ast1' is essentially:
//
//    fn foo(n) { `hello${n}` } // <- definition of first 'foo' is overwritten
//    foo(1)                    // <- notice this will be "hello1" instead of 43,
//                              //    but it is no longer the return value
//    foo("!")                  // returns "hello!"

// Evaluate it
assert_eq!(engine.eval_ast::<String>(&ast1)?, "hello!");

pub fn clear_statements(&mut self) -> &mut AST

Clear all statements in the AST, leaving only function definitions.

pub fn iter_literal_variables( &self, include_constants: bool, include_variables: bool, ) -> impl Iterator<Item = (&str, bool, Dynamic)>

Extract all top-level literal constant and/or variable definitions. This is useful for extracting all global constants from a script without actually running it.

A literal constant/variable definition takes the form of: const VAR = value; and let VAR = value; where value is a literal expression or will be optimized into a literal.

§Example

use rhai::{Engine, Scope};

let engine = Engine::new();

let ast = engine.compile(
"
    const A = 40 + 2;   // constant that optimizes into a literal
    let b = 123;        // literal variable
    const B = b * A;    // non-literal constant
    const C = 999;      // literal constant
    b = A + C;          // expression

    {                   // <- new block scope
        const Z = 0;    // <- literal constant not at top-level

        print(Z);       // make sure the block is not optimized away
    }
")?;

let mut iter = ast.iter_literal_variables(true, false)
                  .map(|(name, is_const, value)| (name, is_const, value.as_int().unwrap()));

assert_eq!(iter.next(), Some(("A", true, 42)));
assert_eq!(iter.next(), Some(("C", true, 999)));
assert_eq!(iter.next(), None);

let mut iter = ast.iter_literal_variables(false, true)
                  .map(|(name, is_const, value)| (name, is_const, value.as_int().unwrap()));

assert_eq!(iter.next(), Some(("b", false, 123)));
assert_eq!(iter.next(), None);

let mut iter = ast.iter_literal_variables(true, true)
                  .map(|(name, is_const, value)| (name, is_const, value.as_int().unwrap()));

assert_eq!(iter.next(), Some(("A", true, 42)));
assert_eq!(iter.next(), Some(("b", false, 123)));
assert_eq!(iter.next(), Some(("C", true, 999)));
assert_eq!(iter.next(), None);

let scope: Scope = ast.iter_literal_variables(true, false).collect();

assert_eq!(scope.len(), 2);

Ok(())