extension methids

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt

@@ -1432,11 +1432,22 @@ class Compiler(
     ): Statement {
         var t = cc.next()
         val start = t.pos
-        val name = if (t.type != Token.Type.ID)
-            throw ScriptError(t.pos, "Expected identifier after 'fn'")
+        var extTypeName: String? = null
+        var name = if (t.type != Token.Type.ID)
+            throw ScriptError(t.pos, "Expected identifier after 'fun'")
         else t.value
 
         t = cc.next()
+        // Is extension?
+        if( t.type == Token.Type.DOT) {
+           extTypeName = name
+           t = cc.next()
+           if( t.type != Token.Type.ID)
+               throw ScriptError(t.pos, "illegal extension format: expected function name")
+            name = t.value
+            t = cc.next()
+        }
+
         if (t.type != Token.Type.LPAREN)
             throw ScriptError(t.pos, "Bad function definition: expected '(' after 'fn ${name}'")
 
@@ -1465,13 +1476,25 @@ class Compiler(
 
             // load params from caller context
             argsDeclaration.assignToContext(context, callerContext.args, defaultAccessType = AccessType.Val)
+            if( extTypeName != null ) {
+                context.thisObj = callerContext.thisObj
+            }
             fnStatements.execute(context)
         }
         return statement(start) { context ->
             // we added fn in the context. now we must save closure
             // for the function
             closure = context
-            context.addItem(name, false, fnBody, visibility)
+            extTypeName?.let { typeName ->
+                // class extension method
+                val type = context.get(typeName)?.value ?: context.raiseSymbolNotFound("class $typeName not found")
+                if( type !is ObjClass ) context.raiseClassCastError("$typeName is not the class instance")
+                type.addFn( name, isOpen = true) {
+                    fnBody.execute(this)
+                }
+            }
+                // regular function/method
+                ?: context.addItem(name, false, fnBody, visibility)
             // as the function can be called from anywhere, we have
             // saved the proper context in the closure
             fnBody

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Context.kt

@@ -72,6 +72,7 @@ open class Context(
         else {
             objects[name]
                 ?: parent?.get(name)
+                ?: thisObj.objClass.getInstanceMemberOrNull(name)
         }
 
     fun copy(pos: Pos, args: Arguments = Arguments.EMPTY, newThisObj: Obj? = null): Context =

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjReal.kt

@@ -64,6 +64,9 @@ data class ObjReal(val value: Double) : Obj(), Numeric {
                     (it.thisObj as ObjReal).value.roundToLong().toObj()
                 },
             )
+            addFn("toInt") {
+                ObjInt(thisAs<ObjReal>().value.toLong())
+            }
         }
     }
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjString.kt

@@ -112,6 +112,7 @@ data class ObjString(val value: String) : Obj() {
                 thisAs<ObjString>().value.uppercase().let(::ObjString)
             }
             addFn("size") { ObjInt(thisAs<ObjString>().value.length.toLong()) }
+            addFn("toReal") { ObjReal(thisAs<ObjString>().value.toDouble())}
         }
     }
 }

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -2284,4 +2284,31 @@ class ScriptTest {
 
         """.trimIndent())
     }
+
+    @Test
+    fun testExtend() = runTest() {
+        eval("""
+            
+            fun Int.isEven() {
+                this % 2 == 0
+            }
+            
+            fun Object.isInteger() {
+                when(this) {
+                    is Int -> true
+                    is Real -> toInt() == this
+                    is String -> toReal().isInteger()
+                    else -> false
+                }
+            }
+            
+            assert( 4.isEven() )
+            assert( !5.isEven() )
+            
+            assert( 12.isInteger() == true )
+            assert( 12.1.isInteger() == false )
+            assert( "5".isInteger() )
+            assert( ! "5.2".isInteger() )
+        """.trimIndent())
+    }
 }