debugging::print builtin

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

src/builtins/debugging.rs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+use crate::ast::Expr;
+use crate::builtins;
+use crate::lexer::Span;
+use crate::value::Value;
+
+use std::collections::HashMap;
+
+use anyhow::Result;
+
+pub fn register(m: &mut HashMap<&'static str, builtins::BuiltinFcn>) {
+    m.insert("print", print);
+}
+
+// Symbol analyzer must ensure that vars used by print are defined before
+// the print statement. Scheduler must ensure the above constraint.
+// Additionally interpreter must allow undefined inputs to print.
+fn print(span: &Span, _params: &[Expr], args: &[Value]) -> Result<Value> {
+    let mut msg = String::default();
+    for a in args {
+        match a {
+            Value::Undefined => msg += "<undefined>",
+            _ => msg += format!("{a}").as_str(),
+        };
+    }
+
+    span.message("print", msg.as_str());
+    Ok(Value::Bool(true))
+}

src/builtins/mod.rs

@@ -1,14 +1,15 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
-pub mod aggregates;
-pub mod arrays;
+mod aggregates;
+mod arrays;
 pub mod comparison;
+mod debugging;
 pub mod numbers;
 pub mod sets;
-pub mod strings;
+mod strings;
 pub mod types;
-pub mod utils;
+mod utils;
 
 use crate::ast::Expr;
 use crate::lexer::Span;
@@ -31,8 +32,30 @@ lazy_static! {
 	aggregates::register(&mut m);
 	arrays::register(&mut m);
 	sets::register(&mut m);
-	types::register(&mut m);
+	//objects::register(&mut m);
 	strings::register(&mut m);
+	//regex::register(&mut m);
+	//glob::register(&mut m);
+	//bitwise::register(&mut m);
+	//conversions::register(&mut m);
+	//units::register(&mut m);
+	types::register(&mut m);
+	//encoding::register(&mut m);
+	//token_signing::register(&mut m);
+	//token_verification::register(&mut m);
+	//time::register(&mut m);
+	//cryptography::register(&mut m);
+	//graphs::register(&mut m);
+	//graphql::register(&mut m);
+	//http::register(&mut m);
+	//cryptography::register(&mut m);
+	//net::register(&mut m);
+	//uuid::register(&mut m);
+	//semantic_versions::register(&mut m);
+	//rego::register(&mut m);
+	//opa::register(&mut m);
+	debugging::register(&mut m);
+	//tracing::register(&mut m);
 	
 	m
     };

src/interpreter.rs

@@ -1187,10 +1187,11 @@ impl<'source> Interpreter<'source> {
         params: &'source Vec<Expr<'source>>,
     ) -> Result<Value> {
         let mut args = vec![];
+        let allow_undefined = name == "print"; // TODO: with modifier
         for p in params {
             match self.eval_expr(p)? {
                 // If any argument is undefined, then the call is undefined.
-                Value::Undefined => return Ok(Value::Undefined),
+                Value::Undefined if !allow_undefined => return Ok(Value::Undefined),
                 p => args.push(p),
             }
         }