Get hello world working again

dust-lang/src/built_in_function.rs

@@ -94,26 +94,26 @@ impl BuiltInFunction {
             (None, None) => {}
         }
 
-        let value_arguments = value_arguments.unwrap();
-
         match self {
-            BuiltInFunction::ToString => Ok(Some(Value::String(value_arguments[0].to_string()))),
+            BuiltInFunction::ToString => {
+                Ok(Some(Value::String(value_arguments.unwrap()[0].to_string())))
+            }
             BuiltInFunction::IsEven => {
-                if let Some(integer) = value_arguments[0].as_integer() {
+                if let Value::Integer(integer) = value_arguments.unwrap()[0] {
                     Ok(Some(Value::Boolean(integer % 2 == 0)))
                 } else {
                     Err(BuiltInFunctionError::ExpectedInteger)
                 }
             }
             BuiltInFunction::IsOdd => {
-                if let Some(integer) = value_arguments[0].as_integer() {
+                if let Value::Integer(integer) = value_arguments.unwrap()[0] {
                     Ok(Some(Value::Boolean(integer % 2 != 0)))
                 } else {
                     Err(BuiltInFunctionError::ExpectedInteger)
                 }
             }
             BuiltInFunction::Length => {
-                if let Value::List(list) = &value_arguments[0] {
+                if let Value::List(list) = &value_arguments.unwrap()[0] {
                     Ok(Some(Value::Integer(list.len() as i64)))
                 } else {
                     Err(BuiltInFunctionError::ExpectedList)
@@ -127,7 +127,7 @@ impl BuiltInFunction {
                 Ok(Some(Value::string(input.trim_end_matches('\n'))))
             }
             BuiltInFunction::WriteLine => {
-                if let Value::String(string) = &value_arguments[0] {
+                if let Value::String(string) = &value_arguments.unwrap()[0] {
                     let mut stdout = stdout();
 
                     stdout.write_all(string.as_bytes())?;

dust-lang/src/core_library.rs

@@ -43,6 +43,15 @@ pub fn core_library<'a>() -> &'a Context {
                     (0, 0),
                 ),
             ),
+            (
+                Identifier::new("read_line"),
+                (
+                    ContextData::VariableValue(Value::Function(Function::BuiltIn(
+                        BuiltInFunction::ReadLine,
+                    ))),
+                    (0, 0),
+                ),
+            ),
             (
                 Identifier::new("write_line"),
                 (

dust-lang/src/vm.rs

@@ -781,7 +781,7 @@ impl Vm {
                     });
                 };
 
-                let mut value_arguments = Vec::new();
+                let mut value_arguments: Option<Vec<Value>> = None;
 
                 for argument in arguments {
                     let position = argument.position();
@@ -789,13 +789,17 @@ impl Vm {
                         .run_expression(argument, collect_garbage)?
                         .expect_value(position)?;
 
-                    value_arguments.push(value);
+                    if let Some(value_arguments) = &mut value_arguments {
+                        value_arguments.push(value);
+                    } else {
+                        value_arguments = Some(vec![value]);
+                    }
                 }
 
                 let context = Context::new();
 
                 function
-                    .call(None, Some(value_arguments), &context)
+                    .call(None, value_arguments, &context)
                     .map(Evaluation::Return)
             }
             _ => Err(RuntimeError::ExpectedValueOrConstructor {

examples/hello_world.ds

@@ -1,6 +1,6 @@
 write_line("Hello, world!")
 write_line("Enter your name...")
 
-name = read_line()
+let name = read_line();
 
 write_line("Hello " + name + "!")