float function

rust/src/eval/function/float.rs

@@ -0,0 +1,23 @@
+use crate::{Error, Result};
+
+pub fn float(args: Vec<serde_json::Value>) -> Result<serde_json::Value> {
+    if let Some(val) = args.get(0) {
+        match val {
+            // serde_json::from_str(pair.as_str());
+            serde_json::Value::Number(num) => match num.as_f64() {
+                Some(float_num) => Ok(serde_json::Value::from(float_num)),
+                None => Err(Error::eval(format!("invalid number {}", num))),
+            },
+            serde_json::Value::String(string) => match string.trim().parse::<f64>() {
+                Ok(val) => Ok(val.into()),
+                Err(err) => Err(Error::eval(err.to_string())),
+            },
+            serde_json::Value::Bool(true) => Ok(serde_json::Value::from(1.0)),
+            serde_json::Value::Bool(false) => Ok(serde_json::Value::from(0.0)),
+            serde_json::Value::Null => Ok(serde_json::Value::from(0.0)),
+            _ => Err(Error::eval("argument does not cast to float".to_string())),
+        }
+    } else {
+        Err(Error::eval("float requires one argument".to_string()))
+    }
+}

rust/src/eval/function/mod.rs

@@ -4,10 +4,12 @@ use std::str::FromStr;
 use crate::eval::expr;
 use crate::{Error, Result, Rule};
 
+mod float;
 mod string;
 
 enum Function {
     Count,
+    Float,
     Log,
     String,
 }
@@ -18,6 +20,7 @@ impl FromStr for Function {
     fn from_str(s: &str) -> Result<Self> {
         match s {
             "count" => Ok(Function::Count),
+            "float" => Ok(Function::Float),
             "log" => Ok(Function::Log),
             "string" => Ok(Function::String),
             _ => Err(Error::query(format!("unknown function {}", s))),
@@ -34,6 +37,7 @@ pub fn eval(pair: Pair<Rule>, context: &serde_json::Value) -> Result<serde_json:
 
     match function {
         Function::Count => count(args),
+        Function::Float => float::float(args),
         Function::Log => log(args),
         Function::String => string::string(args),
     }