Add loading binaries as functions

src/abstract_tree/built_in_value.rs

@@ -103,8 +103,8 @@ impl BuiltInValue {
                     BuiltInFunction::RandomInteger,
                 ] {
                     let key = built_in_function.name().to_string();
-                    let value = Value::Function(Function::BuiltIn(built_in_function));
                     let r#type = built_in_function.r#type();
+                    let value = Value::Function(Function::BuiltIn(built_in_function));
 
                     random_context.insert(key, (value, r#type));
                 }

src/abstract_tree/function_call.rs

@@ -68,21 +68,38 @@ impl AbstractTree for FunctionCall {
             }
         };
 
-        if self.arguments.len() != parameter_types.len() {
+        let required_argument_count =
-            return Err(Error::ExpectedFunctionArgumentAmount {
+            parameter_types.iter().fold(
-                expected: parameter_types.len(),
+                0,
-                actual: self.arguments.len(),
+                |acc, r#type| {
+                    if r#type.is_option() {
+                        acc
+                    } else {
+                        acc + 1
                     }
-            .at_source_position(source, self.syntax_position));
+                },
+            );
+
+        if self.arguments.len() < required_argument_count {
+            return Err(Error::ExpectedFunctionArgumentMinimum {
+                minumum: required_argument_count,
+                actual: self.arguments.len(),
+            });
         }
 
         for (index, expression) in self.arguments.iter().enumerate() {
             if let Some(r#type) = parameter_types.get(index) {
+                let expected_type = expression.expected_type(context)?;
+
+                if let Type::Option(optional_type) = r#type {
+                    optional_type.check(&expected_type)?;
+                } else {
                     r#type
                         .check(&expression.expected_type(context)?)
                         .map_err(|error| error.at_source_position(source, self.syntax_position))?;
                 }
             }
+        }
 
         Ok(())
     }

src/abstract_tree/type.rs

@@ -150,6 +150,10 @@ impl Type {
     pub fn is_map(&self) -> bool {
         matches!(self, Type::Map(_))
     }
+
+    pub fn is_option(&self) -> bool {
+        matches!(self, Type::Option(_))
+    }
 }
 
 impl AbstractTree for Type {

src/built_in_functions/mod.rs

@@ -3,6 +3,7 @@ mod string;
 use std::{
     fmt::{self, Display, Formatter},
     fs::read_to_string,
+    process::Command,
 };
 
 use rand::{random, thread_rng, Rng};
@@ -12,9 +13,10 @@ use crate::{Error, Format, Map, Result, Type, Value};
 
 pub use string::{string_functions, StringFunction};
 
-#[derive(Debug, Copy, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
 pub enum BuiltInFunction {
     AssertEqual,
+    Binary(String),
     FsRead,
     JsonParse,
     Length,
@@ -30,6 +32,7 @@ impl BuiltInFunction {
     pub fn name(&self) -> &'static str {
         match self {
             BuiltInFunction::AssertEqual => "assert_equal",
+            BuiltInFunction::Binary(_) => "binary",
             BuiltInFunction::FsRead => "read",
             BuiltInFunction::JsonParse => "parse",
             BuiltInFunction::Length => "length",
@@ -45,6 +48,10 @@ impl BuiltInFunction {
     pub fn r#type(&self) -> Type {
         match self {
             BuiltInFunction::AssertEqual => Type::function(vec![Type::Any, Type::Any], Type::None),
+            BuiltInFunction::Binary(_) => Type::function(
+                vec![Type::Option(Box::new(Type::String))],
+                Type::Option(Box::new(Type::Integer)),
+            ),
             BuiltInFunction::FsRead => Type::function(vec![Type::String], Type::String),
             BuiltInFunction::JsonParse => Type::function(vec![Type::String], Type::Any),
             BuiltInFunction::Length => Type::function(vec![Type::Collection], Type::Integer),
@@ -67,6 +74,36 @@ impl BuiltInFunction {
 
                 Ok(Value::Boolean(left == right))
             }
+            BuiltInFunction::Binary(binary_name) => {
+                let input = if let Some(value) = arguments.first() {
+                    value.clone()
+                } else {
+                    Value::none()
+                };
+                let mut command = Command::new(binary_name);
+
+                if let Ok(Some(value)) = input.as_option() {
+                    let input_string = value.as_string()?;
+
+                    if !input_string.is_empty() {
+                        command.args(input_string.split_whitespace());
+                    }
+                }
+
+                if let Ok(input_string) = input.as_string() {
+                    if !input_string.is_empty() {
+                        command.args(input_string.split_whitespace());
+                    }
+                }
+
+                let output = command.spawn()?.wait()?;
+                let status_code = match output.code() {
+                    Some(code) => Value::some(Value::Integer(code as i64)),
+                    None => Value::none(),
+                };
+
+                Ok(status_code)
+            }
             BuiltInFunction::FsRead => {
                 Error::expect_argument_amount(self.name(), 1, arguments.len())?;
 

src/error.rs

@@ -83,8 +83,7 @@ pub enum Error {
 
     /// A function was called with the wrong amount of arguments.
     ExpectedFunctionArgumentMinimum {
-        source: String,
+        minumum: usize,
-        minumum_expected: usize,
         actual: usize,
     },
 
@@ -338,14 +337,10 @@ impl fmt::Display for Error {
             ExpectedFunctionArgumentAmount { expected, actual } => {
                 write!(f, "Expected {expected} arguments, but got {actual}.",)
             }
-            ExpectedFunctionArgumentMinimum {
+            ExpectedFunctionArgumentMinimum { minumum, actual } => {
-                source,
-                minumum_expected,
-                actual,
-            } => {
                 write!(
                     f,
-                    "{source} expected at least {minumum_expected} arguments, but got {actual}."
+                    "Expected at least {minumum} arguments, but got {actual}."
                 )
             }
             ExpectedString { actual } => {

src/main.rs

@@ -10,7 +10,7 @@ use reedline::{
 
 use std::{fs::read_to_string, path::PathBuf};
 
-use dust_lang::{built_in_values, Interpreter, Map, Result, Value};
+use dust_lang::{built_in_values, Function, Interpreter, Map, Result, Value};
 
 /// Command-line arguments to be parsed.
 #[derive(Parser, Debug)]
@@ -171,6 +171,31 @@ impl Highlighter for DustHighlighter {
 }
 
 fn run_shell(context: Map) -> Result<()> {
+    for (key, value) in std::env::vars() {
+        if key == "PATH" {
+            for path in value.split([' ', ':']) {
+                let path_dir = if let Ok(path_dir) = PathBuf::from(path).read_dir() {
+                    path_dir
+                } else {
+                    continue;
+                };
+
+                for entry in path_dir {
+                    let entry = entry?;
+
+                    if entry.file_type()?.is_file() {
+                        context.set(
+                            entry.file_name().to_string_lossy().to_string(),
+                            Value::Function(Function::BuiltIn(dust_lang::BuiltInFunction::Binary(
+                                entry.file_name().to_string_lossy().to_string(),
+                            ))),
+                        )?;
+                    }
+                }
+            }
+        }
+    }
+
     let mut interpreter = Interpreter::new(context.clone());
     let prompt = DefaultPrompt::default();
     let mut keybindings = default_emacs_keybindings();