Struct arithmetic_eval::fns::If

pub struct If;

if function that eagerly evaluates “if” / “else” terms.

Type

(using arithmetic-typing notation)

(Bool, 'T, 'T) -> 'T

Examples

let program = "x = 3; if(x == 2, -1, x + 1)";
let program = Untyped::<F32Grammar>::parse_statements(program)?;
let module = ExecutableModule::new("test_if", &program)?;

let mut env = Environment::new();
env.insert_native_fn("if", fns::If);
assert_eq!(module.with_env(&env)?.run()?, Value::Prim(4.0));

You can also use the lazy evaluation by returning a function and evaluating it afterwards:

let program = "x = 3; if(x == 2, || -1, || x + 1)()";
let program = Untyped::<F32Grammar>::parse_statements(program)?;
let module = ExecutableModule::new("test_if", &program)?;

let mut env = Environment::new();
env.insert_native_fn("if", fns::If);
assert_eq!(module.with_env(&env)?.run()?, Value::Prim(4.0));

Trait Implementations

impl Clone for If

fn clone(&self) -> If

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for If

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

Formats the value using the given formatter.

impl Default for If

fn default() -> If

Returns the “default value” for a type.

impl<T> NativeFn<T> for If

fn evaluate( &self, args: Vec<SpannedValue<T>>, ctx: &mut CallContext<'_, T>, ) -> EvalResult<T>

Executes the function on the specified arguments.

impl Copy for If