conversion::to_number builtin

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

src/builtins/conversions.rs

@@ -0,0 +1,40 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+use crate::ast::Expr;
+use crate::builtins;
+use crate::builtins::utils::ensure_args_count;
+use crate::lexer::Span;
+use crate::value::Value;
+
+use std::collections::HashMap;
+
+use anyhow::{bail, Result};
+
+pub fn register(m: &mut HashMap<&'static str, builtins::BuiltinFcn>) {
+    m.insert("to_number", to_number);
+}
+
+fn to_number(span: &Span, params: &[Expr], args: &[Value]) -> Result<Value> {
+    let name = "to_number";
+    ensure_args_count(span, name, params, args, 1)?;
+
+    let span = params[0].span();
+    Ok(match &args[0] {
+        Value::Bool(true) => Value::from_float(1.0),
+        Value::Bool(false) => Value::from_float(0.0),
+        Value::Number(_) => args[0].clone(),
+        // Eventhough the doc says that strings are converted using strconv.Atoi golang method,
+        // in practice strings seems to be read as json numbers. This means that floating point
+        // numbers are read and the string representation is limited to what json allows.
+        Value::String(s) => match Value::from_json_str(s) {
+            Ok(Value::Number(n)) => Value::Number(n),
+            _ => {
+                bail!(span.error("could not parse string as number"));
+            }
+        },
+        _ => {
+            bail!(span.error(format!("`{name}` expects bool/number/string argument.").as_str()));
+        }
+    })
+}

src/builtins/mod.rs

@@ -5,6 +5,7 @@ mod aggregates;
 mod arrays;
 mod bitwise;
 pub mod comparison;
+mod conversions;
 mod debugging;
 pub mod numbers;
 pub mod sets;
@@ -39,7 +40,7 @@ lazy_static! {
 	//regex::register(&mut m);
 	//glob::register(&mut m);
 	bitwise::register(&mut m);
-	//conversions::register(&mut m);
+	conversions::register(&mut m);
 	//units::register(&mut m);
 	types::register(&mut m);
 	//encoding::register(&mut m);