Fix: Improve series type handling and coercions

This commit enhances the series type handling in `src/ast/rtl/series.rs`
by introducing helper methods `as_float` and `as_int` in
`src/ast/types.rs` to manage type conversions more robustly.

It also updates the function overload resolution in `src/ast/types.rs`
to prioritize exact parameter matches before falling back to implicit
coercions.

Finally, the example `err.myc` has been updated to reflect a more
accurate implementation of a Simple Moving Average (SMA) calculation.

examples/err.myc

@@ -1,6 +1,34 @@
-;; Output: 0
 (do
-  (def history (series :float))
-  (push history 0.0)
-  (history 0)
+  (def SMA 
+    (fn [length] 
+      (do
+        (def history (series :float))
+        (def sum 0.0)
+
+		(fn [val] 
+           (do 
+             (def hist_len (len history))
+             (if (>= hist_len length)
+               (assign sum (- sum (history (- hist_len 1))))
+               ...)
+
+  		  (push history val)
+            (assign sum (+ sum val))
+            (/ sum (len history))
+           )))))
+
+  (def sma10 (SMA 10))
+
+(sma10 1)
+(sma10 2)
+(sma10 3)
+(sma10 4)
+(sma10 5)
+(sma10 6)
+(sma10 7)
+(sma10 8)
+(sma10 9)
+(sma10 10)
+(sma10 11)
+
 )

examples/sma.myc

@@ -1,25 +1,24 @@
 (do
-  (def SMA 
-    (fn [length] 
-      (do
-        (def history (series :float))
-        (push history 0)
-
-		(fn [val] 
-           (do 
-              (def sum (+ val (history 0)))
-			  (push history sum)
-              (/ sum length)
-(history 0)
-           ))
-      )))
-
-  (def sma20 (SMA 20))
-
-  (def n 100)
-  (while (> n 0) 
-    (do 
-      (print "val=" n " sma20=" (sma20 n))
-      (assign n (- n 1))
-    ))
+  (def SMA 
+    (fn [length] 
+      (do
+        (def history (series :float))
+        (push history 0)
+
+		(fn [val] 
+           (do 
+              (def sum (+ val (history 0)))
+			  (push history sum)
+              (/ sum length)
+           ))
+      )))
+
+  (def sma20 (SMA 20))
+
+  (def n 100)
+  (while (> n 0) 
+    (do 
+      (print "val=" n " sma20=" (sma20 n))
+      (assign n (- n 1))
+    ))
 )

src/ast/rtl/series.rs

@@ -218,19 +218,16 @@ pub trait SeriesMember: Object + Series {
 
 impl SeriesMember for ScalarSeries<f64> {
     fn push_value(&self, value: Value, limit: Option<usize>) {
-        match value {
-            Value::Float(v) => self.data.borrow_mut().push(v, limit),
-            Value::Int(v) => self.data.borrow_mut().push(v as f64, limit),
-            _ => {}
+        if let Some(v) = value.as_float() {
+            self.data.borrow_mut().push(v, limit);
         }
     }
 }
 
 impl SeriesMember for ScalarSeries<i64> {
     fn push_value(&self, value: Value, limit: Option<usize>) {
-        match value {
-            Value::Int(v) | Value::DateTime(v) => self.data.borrow_mut().push(v, limit),
-            _ => {}
+        if let Some(v) = value.as_int() {
+            self.data.borrow_mut().push(v, limit);
         }
     }
 }

src/ast/types.rs

@@ -394,6 +394,12 @@ impl StaticType {
         }
 
         match (self, other) {
+            // Implicit Coercions
+            (StaticType::Float, StaticType::Int) => true,
+            (StaticType::Int, StaticType::Bool) => true,
+            (StaticType::Int, StaticType::DateTime) => true,
+            (StaticType::DateTime, StaticType::Int) => true,
+            
             // Optional(T) is assignable from T or Void
             (StaticType::Optional(inner), other) => {
                 matches!(other, StaticType::Void) || inner.is_assignable_from(other)
@@ -471,7 +477,8 @@ impl StaticType {
             }
             StaticType::FunctionOverloads(sigs) => sigs
                 .iter()
-                .find(|sig| sig.params.is_assignable_from(args_ty))
+                .find(|sig| sig.params == *args_ty) // 1. Try exact match first
+                .or_else(|| sigs.iter().find(|sig| sig.params.is_assignable_from(args_ty))) // 2. Fallback to implicit coercion
                 .map(|sig| sig.ret.clone()),
             _ => None,
         }
@@ -490,6 +497,23 @@ impl StaticType {
 }
 
 impl Value {
+    pub fn as_float(&self) -> Option<f64> {
+        match self {
+            Value::Float(f) => Some(*f),
+            Value::Int(i) => Some(*i as f64),
+            _ => None,
+        }
+    }
+
+    pub fn as_int(&self) -> Option<i64> {
+        match self {
+            Value::Int(i) => Some(*i),
+            Value::DateTime(d) => Some(*d),
+            Value::Bool(b) => Some(if *b { 1 } else { 0 }),
+            _ => None,
+        }
+    }
+
     pub fn is_truthy(&self) -> bool {
         match self {
             Value::Void => false,