feat: stronger typing for algorithmic function handler

Author: fkleon

CHANGELOG.md

@@ -27,6 +27,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - The `Root`function now accepts an `Expression` as degree.
+- Handler functions passed to `AlgorithmicFunction` can no longer be
+  dynamically typed.
 
 ### Deprecated
 

lib/src/functions.dart

@@ -1111,7 +1111,7 @@ class AlgorithmicFunction extends DefaultFunction {
   /// method instead it is supported by the parser.
   AlgorithmicFunction(super.name, super.args, this.handler) : super._any();
 
-  Function handler;
+  double Function(List<double>) handler;
 
   @override
   dynamic evaluate(EvaluationType type, ContextModel context) {

lib/src/parser.dart

@@ -19,7 +19,8 @@ abstract class ExpressionParser {
   ///
   /// Throws a [FormatException] if the given [name] is already defined and
   /// [replace] is false.
-  void addFunction(String name, dynamic handler, {bool replace = false});
+  void addFunction(String name, double Function(List<double>) handler,
+      {bool replace = false});
 }
 
 /// The default parser. This type alias is deprecated, use [GrammarParser]
@@ -175,7 +176,8 @@ class ShuntingYardParser implements ExpressionParser {
   }
 
   @override
-  void addFunction(String name, dynamic handler, {bool replace = false}) {
+  void addFunction(String name, double Function(List<double>) handler,
+      {bool replace = false}) {
     if (lex.keywords.containsKey(name) && !replace) {
       throw FormatException('Cannot redefine existing function $name');
     }

lib/src/parser_petit.dart

@@ -50,7 +50,7 @@ class GrammarParser implements ExpressionParser {
   };
 
   /// Dynamically defined algorithmic functions.
-  final functionsC = <String, dynamic>{};
+  final functionsC = <String, double Function(List<double>)>{};
 
   /// Creates an expression from the given identifier, and list of arguments.
   /// May return a constant, function or variable.
@@ -79,7 +79,7 @@ class GrammarParser implements ExpressionParser {
       default:
         var fun = functionsC[name];
         if (fun != null) {
-          return AlgorithmicFunction(name, arguments, functionsC[name]);
+          return AlgorithmicFunction(name, arguments, fun);
         }
     }
 
@@ -172,7 +172,8 @@ class GrammarParser implements ExpressionParser {
   }
 
   @override
-  void addFunction(String name, dynamic handler, {bool replace = false}) {
+  void addFunction(String name, double Function(List<double>) handler,
+      {bool replace = false}) {
     if (functionsC.containsKey(name) && !replace) {
       throw FormatException('Cannot redefine existing function $name');
     }

test/expression_test_set.dart

@@ -1359,7 +1359,7 @@ class ExpressionTests extends TestSet {
 
   /// Tests creation of algorithmic functions.
   void algorithmicFunctionCreation() {
-    dynamic handler = (List<double> args) => args.reduce(math.min);
+    handler(List<double> args) => args.reduce(math.min);
 
     // Generic list minimum (R^2 -> R)
     AlgorithmicFunction f = AlgorithmicFunction('my_min', [n1, -n1], handler);
@@ -1374,7 +1374,7 @@ class ExpressionTests extends TestSet {
     ContextModel cm = ContextModel();
 
     Variable x = Variable('x');
-    dynamic handler = (List<double> args) => args.reduce(math.min);
+    handler(List<double> args) => args.reduce(math.min);
 
     // Generic list minimum (R^3 -> R)
     AlgorithmicFunction f =

test/parser_petit_test_set.dart

@@ -275,13 +275,13 @@ class PetitParserTests extends TestSet {
 
   void parseAlgorithmicFunctions() {
     var cases = {
-      'myAlgorithmicFunction(1.0)': AlgorithmicFunction(
-          'myAlgorithmicFunction', [Number(1.0)], () => null),
+      'myAlgorithmicFunction(1.0)':
+          AlgorithmicFunction('myAlgorithmicFunction', [Number(1.0)], (_) => 0),
       'my_min(1,x,-2)': AlgorithmicFunction('my_min',
-          [Number(1), Variable('x'), UnaryMinus(Number(2))], () => null),
+          [Number(1), Variable('x'), UnaryMinus(Number(2))], (_) => 0),
     };
 
-    parser.addFunction('myAlgorithmicFunction', () => null, replace: true);
+    parser.addFunction('myAlgorithmicFunction', (_) => 0, replace: true);
     parser.addFunction('my_min', (List<double> args) => args.reduce(math.min),
         replace: true);
 

test/parser_test_set.dart

@@ -226,13 +226,13 @@ class ParserTests extends TestSet {
 
   void parseAlgorithmicFunctions() {
     var cases = {
-      'myAlgorithmicFunction(1.0)': AlgorithmicFunction(
-          'myAlgorithmicFunction', [Number(1.0)], () => null),
+      'myAlgorithmicFunction(1.0)':
+          AlgorithmicFunction('myAlgorithmicFunction', [Number(1.0)], (_) => 0),
       'my_min(1,x,-2)': AlgorithmicFunction('my_min',
-          [Number(1), Variable('x'), UnaryMinus(Number(2))], () => null),
+          [Number(1), Variable('x'), UnaryMinus(Number(2))], (_) => 0),
     };
 
-    parser.addFunction('myAlgorithmicFunction', () => null, replace: true);
+    parser.addFunction('myAlgorithmicFunction', (_) => 0, replace: true);
     parser.addFunction('my_min', (List<double> args) => args.reduce(math.min),
         replace: true);