add print function

crates/interpreter/src/eval/builtin.rs

@@ -1,5 +1,6 @@
 mod last;
 mod len;
+mod print;
 mod push;
 mod rest;
 
@@ -13,10 +14,11 @@ pub struct BuiltInFunctionObject {
 
 pub(crate) fn lookup_builtins(identifier: &str) -> Option<Object> {
     match identifier {
-        "len" => create_builtin("len", len::len),
-        "last" => create_builtin("last", last::last),
-        "rest" => create_builtin("rest", rest::rest),
-        "push" => create_builtin("push", push::push),
+        print::FN_NAME => create_builtin(print::FN_NAME, print::print),
+        len::FN_NAME => create_builtin(len::FN_NAME, len::len),
+        last::FN_NAME => create_builtin(last::FN_NAME, last::last),
+        rest::FN_NAME => create_builtin(rest::FN_NAME, rest::rest),
+        push::FN_NAME => create_builtin(push::FN_NAME, push::push),
         _ => None,
     }
 }

crates/interpreter/src/eval/builtin/last.rs

@@ -1,6 +1,6 @@
 use crate::eval::{eval_error::EvalError, objects::Object};
 
-const FN_NAME: &str = "last";
+pub const FN_NAME: &str = "last";
 pub fn last(args: &[Object]) -> Result<Object, EvalError> {
     if args.len() != 1 {
         return Err(EvalError::BuiltInInvalidArguments(

crates/interpreter/src/eval/builtin/len.rs

@@ -5,10 +5,11 @@ use crate::eval::{
     objects::{Object, PrimitiveObject},
 };
 
+pub const FN_NAME: &str = "len";
 pub fn len(args: &[Object]) -> Result<Object, EvalError> {
     if args.len() != 1 {
         return Err(EvalError::BuiltInInvalidArguments(
-            "len".to_string(),
+            FN_NAME.to_owned(),
             format!("Expected 1 argument, got {}", args.len()),
         ));
     }
@@ -23,7 +24,7 @@ pub fn len(args: &[Object]) -> Result<Object, EvalError> {
             Ok(Object::primitive_from_int(string.len() as i32))
         }
         _ => Err(EvalError::BuiltInInvalidArguments(
-            "len".to_string(),
+            FN_NAME.to_owned(),
             "Expected a string or array".to_string(),
         )),
     }

crates/interpreter/src/eval/builtin/print.rs

@@ -0,0 +1,10 @@
+use crate::eval::{eval_error::EvalError, objects::Object};
+
+pub const FN_NAME: &str = "print";
+pub fn print(args: &[Object]) -> Result<Object, EvalError> {
+    for arg in args {
+        println!("{}", arg);
+    }
+
+    Ok(Object::Void)
+}

crates/interpreter/src/eval/builtin/push.rs

@@ -1,6 +1,6 @@
 use crate::eval::{eval_error::EvalError, objects::Object};
 
-const FN_NAME: &str = "push";
+pub const FN_NAME: &str = "push";
 pub fn push(args: &[Object]) -> Result<Object, EvalError> {
     if args.len() != 2 {
         return Err(EvalError::BuiltInInvalidArguments(

crates/interpreter/src/eval/builtin/rest.rs

@@ -1,6 +1,6 @@
 use crate::eval::{eval_error::EvalError, objects::Object};
 
-const FN_NAME: &str = "rest";
+pub const FN_NAME: &str = "rest";
 pub fn rest(args: &[Object]) -> Result<Object, EvalError> {
     if args.len() != 1 {
         return Err(EvalError::BuiltInInvalidArguments(

crates/interpreter/tests/builtins.rs

@@ -1,4 +1,9 @@
-use interpreter::eval::{self, eval_error::EvalError, objects::Environment, EvaledProgram};
+use interpreter::eval::{
+    self,
+    eval_error::EvalError,
+    objects::{Environment, Object},
+    EvaledProgram,
+};
 
 mod common;
 
@@ -106,3 +111,16 @@ fn len_error_test() {
         }
     }
 }
+
+#[test]
+fn print_prints() {
+    let input = r#"print("Hello world")"#;
+
+    let scope = &mut Environment::new_env_reference();
+    let object = eval::eval(input, scope);
+
+    match object {
+        EvaledProgram::Valid(Object::Void) => {}
+        _ => panic!("Expected valid program"),
+    }
+}