fix #15, default toString for a class

+default comparison for a class
!give up struct in favor of class (simpler)

docs/OOP.md

@@ -141,7 +141,24 @@ set at construction but not available outside the class:
     void
     >>> void
 
+## Default class methods
 
+In many cases it is necessary to implement custom comparison and `toString`, still
+each class is provided with default implementations:
+
+- default toString outputs class name and its _public_ fields.
+- default comparison compares compares all public fields in order of appearance.
+
+For example, for our class Point:
+
+    class Point(x,y)
+    assert( Point(1,2) == Point(1,2) )
+    assert( Point(1,2) !== Point(1,2) )
+    assert( Point(1,2) != Point(1,3) )
+    assert( Point(1,2) < Point(2,2) )
+    assert( Point(1,2) < Point(1,3) )
+    Point(1,1+1)
+    >>> Point(1, 2)
 
 # Theory
 

docs/declaring_arguments.md

@@ -1,7 +1,7 @@
 # Declaring arguments in Lyng
 
 It is a common thing that occurs in many places in Lyng, function declarations, 
-lambdas, struct and class declarations.
+lambdas and class declarations.
 
 ## Regular
 

library/src/commonMain/kotlin/net/sergeych/lyng/ObjInstance.kt

@@ -26,4 +26,23 @@ class ObjInstance(override val objClass: ObjClass) : Obj() {
         if( name in publicFields ) return instanceContext[name]!!.value.invoke(context, this, args)
         return super.invokeInstanceMethod(context, name, args)
     }
+
+    override fun toString(): String {
+        val fields = publicFields.map {
+                instanceContext[it]?.value?.toString() ?: "??"
+        }.joinToString(", ")
+        return "${objClass.className}($fields)"
+    }
+
+    override suspend fun compareTo(context: Context, other: Obj): Int {
+        if( other !is ObjInstance ) return -1
+        if( other.objClass != objClass ) return -1
+        for( f in publicFields ) {
+            val a = instanceContext[f]!!.value
+            val b = other.instanceContext[f]!!.value
+            val d = a.compareTo(context, b)
+            if (d != 0) return d
+        }
+        return 0
+    }
 }

library/src/commonTest/kotlin/ScriptTest.kt

@@ -1386,7 +1386,7 @@ class ScriptTest {
     fun testSimpleStruct() = runTest {
         val c = Context()
         c.eval("""
-            struct Point(x,y)
+            class Point(x,y)
             assert( Point::class is Class )
             val p = Point(2,3)
             assert(p is Point)
@@ -1405,7 +1405,7 @@ class ScriptTest {
     fun testNonAssignalbeFieldInStruct() = runTest {
         val c = Context()
         c.eval("""
-            struct Point(x,y)
+            class Point(x,y)
             val p = Point("2",3)
             assert(p is Point)
             assert( p.x == "2" )
@@ -1420,7 +1420,7 @@ class ScriptTest {
     fun testStructBodyVal() = runTest {
         val c = Context()
         c.eval("""
-            struct Point(x,y) {
+            class Point(x,y) {
                 val length = sqrt(x*x+y*y)
                 var foo = "zero"
             }
@@ -1440,7 +1440,7 @@ class ScriptTest {
     fun testStructBodyFun() = runTest {
         val c = Context()
         c.eval("""
-            struct Point(x,y) {
+            class Point(x,y) {
                 fun length() { 
                     sqrt(x*x+y*y) 
                 }
@@ -1487,4 +1487,30 @@ class ScriptTest {
             assertEquals( 1, cond { 1 } )
         """.trimIndent())
     }
+
+    @Test
+    fun testClasstoString() = runTest {
+        eval("""
+            class Point {
+                var x
+                var y
+            }
+            val p = Point()
+            p.x = 1
+            p.y = 2
+            println(p)
+        """.trimIndent())
+    }
+
+    @Test
+    fun testClassDefaultCompare() = runTest {
+        eval("""
+            class Point(x,y)
+            assert( Point(1,2) == Point(1,2) )
+            assert( Point(1,2) !== Point(1,2) )
+            assert( Point(1,2) != Point(1,3) )
+            assert( Point(1,2) < Point(2,2) )
+            assert( Point(1,2) < Point(1,3) )
+        """.trimIndent())
+    }
 }