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))
+}