v0.5.1-SNAPSHOT: Exceptions Handling!

+shortcut throw "message"

docs/exceptions_handling.md

@@ -0,0 +1,129 @@
+# Exceptions handling
+
+Exceptions are widely used in modern programming languages, so
+they are implemented also in Lyng and in the most complete way.
+
+# Exception classes
+
+Exceptions are throwing instances of some class that inherits `Exception`
+across the code. Below is the list of built-in exceptions. Note that
+only objects that inherit `Exception` can be thrown. For example:
+
+    assert( IllegalArgumentException() is Exception)
+    >>> void
+
+# Try statement: catching exceptions
+
+There general pattern is:
+
+```
+try_statement = try_clause, [catch_clause, ...], [finally_clause] 
+
+try_clause = "try", "{", statements, "}"
+
+catch_clause = "catch", [(full_catch | shorter_catch)], "{", statements "}"
+
+full_catch = "(", catch_var, ":", exception_class [, excetpion_class...], ")
+
+shorter_catch = "(", catch_var, ")"
+
+finally_clause = "{", statements, "}"
+```
+
+Let's in details.
+
+## Full catch block:
+
+    val result = try {
+        throw IllegalArgumentException("the test")
+    }
+    catch( x: IndexOutOfBoundsException, IllegalArgumentException) {
+        x.message
+    }
+    catch(x: Exception) {
+        "bad"
+    }
+    assertEquals(result, "the test")
+    >>> void
+
+Because our exception is listed in a first catch block, it is processed there.
+
+The full form allow a single catch block to process exceptions with specified classes and bind actual caught object to
+the given variable. This is most common and well known form, implemented like this or similar in many other languages,
+like Kotlin, Java or C++.
+
+## Shorter form
+
+When you want to catch _all_ the exceptions, you should write `catch(e: Exception)`,
+but it is somewhat redundant, so there is simpler variant:
+
+    val sample2 = try {
+        throw IllegalArgumentException("sample 2")
+    }
+    catch(x) {
+        x.message
+    }
+    assertEquals( sample2, "sample 2" )
+    >>> void
+
+But well most likely you will find default variable `it`, like in Kotlin, more than enough
+to catch all exceptions to, then you can write it even shorter:
+
+    val sample2 = try {
+        throw IllegalArgumentException("sample 3")
+    }
+    catch {
+        it.message
+    }
+    assertEquals( sample2, "sample 3" )
+    >>> void
+
+You can even check the type of the `it` and create more convenient and sophisticated processing logic. Such approach is
+used, for example, in Scala.
+
+# Conveying data with exceptions
+
+The simplest way is to provide exception string and `Exception` class:
+
+    try {
+        throw Exception("this is my exception")
+    }
+    catch {
+        it.message
+    }
+    >>> "this is my exception"
+
+This way, in turn, can also be shortened, as it is overly popular:
+
+    try {
+        throw "this is my exception"
+    }
+    catch {
+        it.message
+    }
+    >>> "this is my exception"
+
+The trick, though, works with strings only, and always provide `Exception` instances, which is good for debugging but
+most often not enough.
+
+# Custom error classes
+
+_this functionality is not yet released_
+
+# Standard exception classes
+
+| class                      | notes                                                 |
+|----------------------------|-------------------------------------------------------|
+| Exception                  | root of al throwable objects                          |
+| NullPointerException       |                                                       |
+| AssertionFailedException   |                                                       | 
+| ClassCastException         |                                                       |
+| IndexOutOfBoundsException  |                                                       |
+| IllegalArgumentException   |                                                       | 
+| IllegalAssignmentException | assigning to val, etc.                                |
+| SymbolNotDefinedException  |                                                       |
+| IterationEndException      | attempt to read iterator past end, `hasNext == false` |
+| AccessException            | attempt to access private members or like             |
+| UnknownException           | unexpected kotlin exception caught                    |
+|                            |                                                       |
+

docs/tutorial.md

@@ -12,7 +12,7 @@ In other word, the code usually works as expected when you see it. So, nothing u
 __Other documents to read__ maybe after this one:
 
 - [Advanced topics](advanced_topics.md), [declaring arguments](declaring_arguments.md)
-- [OOP notes](OOP.md)
+- [OOP notes](OOP.md), [exception handling](exceptions_handling.md)
 - [math in Lyng](math.md)
 - Some class references: [List], [Real], [Range], [Iterable], [Iterator]
 - Some samples: [combinatorics](samples/combinatorics.lyng.md), national vars and loops: [сумма ряда](samples/сумма_ряда.lyng.md). More at [samples folder](samples)
@@ -753,6 +753,62 @@ We can use labels too:
     assert( search(["hello", "world"], 'z') == null)
     >>> void
 
+# Exception handling
+
+Very much like in Kotlin. Try block returns its body block result, if no exception was cauht, or the result from the catch block that caught the exception:
+
+    var error = "not caught"
+    var finallyCaught = false
+    val result = try {
+        throw IllegalArgumentException()
+        "invalid"
+    }
+    catch(nd: SymbolNotDefinedException) {
+        error = "bad catch"
+    }
+    catch(x: IllegalArgumentException) {
+        error = "no error"
+        "OK"
+    }
+    finally {
+        // finally does not affect returned value
+        "too bad"
+    }
+    assertEquals( "no error", error)
+    assertEquals( "OK", result)
+    >>> void
+
+There is shorter form of catch block when you want to catch any exception:
+
+    var caught = null
+    try {
+        throw IllegalArgumentException()
+    }
+    catch(t) { // same as catch(t: Exception), but simpler
+        caught = t
+    }
+    assert( caught is IllegalArgumentException )
+    >>> void
+
+And even shortest, for the Lying lang tradition, missing var is `it`:
+
+    var caught = null
+    try {
+        throw IllegalArgumentException()
+    }
+    catch { // same as catch(it: Exception), but simpler
+        caught = it
+    }
+    assert( caught is IllegalArgumentException )
+    >>> void
+
+It is possible to catch several exceptions in the same block too, use 
+`catch( varName: ExceptionClass1, ExceptionClass2)`, etc, use short form of throw and
+many more.
+
+- see [exception handling](exceptions_handling.md) for detailed exceptions tutorial and reference.
+
+
 # Self-assignments in expression
 
 There are auto-increments and auto-decrements:

library/build.gradle.kts

@@ -5,7 +5,7 @@ import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 group = "net.sergeych"
-version = "0.4.0-SNAPSHOT"
+version = "0.5.1-SNAPSHOT"
 
 buildscript {
     repositories {
@@ -62,6 +62,7 @@ kotlin {
     sourceSets {
         all {
             languageSettings.optIn("kotlinx.coroutines.ExperimentalCoroutinesApi")
+            languageSettings.optIn("kotlin.contracts.ExperimentalContracts::class")
             languageSettings.optIn("kotlin.ExperimentalUnsignedTypes")
             languageSettings.optIn("kotlin.coroutines.DelicateCoroutinesApi")
         }

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

@@ -717,10 +717,132 @@ class Compiler(
         "fn", "fun" -> parseFunctionDeclaration(cc)
         "if" -> parseIfStatement(cc)
         "class" -> parseClassDeclaration(cc, false)
-        "struct" -> parseClassDeclaration(cc, true)
+        "try" -> parseTryStatement(cc)
+        "throw" -> parseThrowStatement(cc)
         else -> null
     }
 
+    private fun parseThrowStatement(cc: CompilerContext): Statement {
+        val throwStatement = parseStatement(cc) ?: throw ScriptError(cc.currentPos(), "throw object expected")
+        return statement {
+            var errorObject = throwStatement.execute(this)
+            if( errorObject is ObjString )
+                errorObject = ObjException(this, errorObject.value)
+            if( errorObject is ObjException )
+                raiseError(errorObject)
+            else raiseError("this is not an exception object: $errorObject")
+        }
+    }
+
+    private data class CatchBlockData(
+        val catchVar: Token,
+        val classNames: List<String>,
+        val block: Statement
+    )
+
+    private fun parseTryStatement(cc: CompilerContext): Statement {
+        val body = parseBlock(cc)
+        val catches = mutableListOf<CatchBlockData>()
+        cc.skipTokens(Token.Type.NEWLINE)
+        var t = cc.next()
+        while( t.value == "catch" ) {
+
+            if (cc.skipTokenOfType(Token.Type.LPAREN, isOptional = true)) {
+                t = cc.next()
+                if (t.type != Token.Type.ID) throw ScriptError(t.pos, "expected catch variable")
+                val catchVar = t
+
+                val exClassNames = mutableListOf<String>()
+                if (cc.skipTokenOfType(Token.Type.COLON, isOptional = true)) {
+                    // load list of exception classes
+                    do {
+                        t = cc.next()
+                        if (t.type != Token.Type.ID)
+                            throw ScriptError(t.pos, "expected exception class name")
+                        exClassNames += t.value
+                        t = cc.next()
+                        when (t.type) {
+                            Token.Type.COMMA -> {
+                                continue
+                            }
+
+                            Token.Type.RPAREN -> {
+                                break
+                            }
+
+                            else -> throw ScriptError(t.pos, "syntax error: expected ',' or ')'")
+                        }
+                    } while (true)
+                } else {
+                    // no type!
+                    exClassNames += "Exception"
+                    cc.skipTokenOfType(Token.Type.RPAREN)
+                }
+                val block = parseBlock(cc)
+                catches += CatchBlockData(catchVar, exClassNames, block)
+                cc.skipTokens(Token.Type.NEWLINE)
+                t = cc.next()
+            } else {
+                // no (e: Exception) block: should be shortest variant `catch { ... }`
+                cc.skipTokenOfType(Token.Type.LBRACE, "expected catch(...) or catch { ... } here")
+                catches += CatchBlockData(Token("it", cc.currentPos(), Token.Type.ID), listOf("Exception"),
+                    parseBlock(cc,true))
+                t = cc.next()
+            }
+        }
+        if( catches.isEmpty() )
+            throw ScriptError(cc.currentPos(), "try block must have at least one catch clause")
+        val finallyClause = if( t.value == "finally" ) {
+            parseBlock(cc)
+        } else {
+            cc.previous()
+            null
+        }
+
+        return statement {
+            var result: Obj = ObjVoid
+            try {
+                // body is a parsed block, it already has separate context
+                result = body.execute(this)
+            }
+            catch (e: Exception) {
+                // convert to appropriate exception
+                val objException = when(e) {
+                    is ExecutionError -> e.errorObject
+                    else -> ObjUnknownException(this, e.message ?: e.toString())
+                }
+                // let's see if we should catch it:
+                var isCaught = false
+                for( cdata in catches ) {
+                    var exceptionObject: ObjException? = null
+                    for (exceptionClassName in cdata.classNames) {
+                        val exObj = ObjException.getErrorClass(exceptionClassName)
+                            ?: raiseSymbolNotFound("error clas not exists: $exceptionClassName")
+                        if( objException.isInstanceOf(exObj) ) {
+                            exceptionObject = objException
+                            break
+                        }
+                    }
+                    if( exceptionObject != null ) {
+                        val catchContext = this.copy(pos = cdata.catchVar.pos)
+                        catchContext.addItem(cdata.catchVar.value, false, objException)
+                        result = cdata.block.execute(catchContext)
+                        isCaught = true
+                        break
+                    }
+                }
+                // rethrow if not caught this exception
+                if( !isCaught )
+                    throw e
+            }
+            finally {
+                // finally clause does not alter result!
+                finallyClause?.execute(this)
+            }
+            result
+        }
+    }
+
     private fun parseClassDeclaration(cc: CompilerContext, isStruct: Boolean): Statement {
         val nameToken = cc.requireToken(Token.Type.ID)
         val constructorArgsDeclaration =
@@ -906,9 +1028,10 @@ class Compiler(
                 } catch (lbe: LoopBreakContinueException) {
                     if (lbe.label == label || lbe.label == null) {
                         if (lbe.doContinue) continue
-                    }
                         return lbe.result
                     }
+                    throw lbe
+                }
             }
         } else {
             for (i in start.toLong()..<end.toLong()) {
@@ -934,9 +1057,10 @@ class Compiler(
                 } catch (lbe: LoopBreakContinueException) {
                     if (lbe.label == label || lbe.label == null) {
                         if (lbe.doContinue) continue
-                    }
                         return lbe.result
                     }
+                    throw lbe
+                }
             else {
                 loopVar.value = iterObj.invokeInstanceMethod(forContext, "next")
                 result = body.execute(forContext)
@@ -991,6 +1115,7 @@ class Compiler(
                             break
                         }
                     }
+                    throw e
                 }
             } while( condition.execute(doContext).toBool() )
             if( !wasBroken ) elseStatement?.let { s -> result = s.execute(it) }

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

@@ -16,27 +16,27 @@ class Context(
     fun raiseNotImplemented(what: String = "operation"): Nothing = raiseError("$what is not implemented")
 
     @Suppress("unused")
-    fun raiseNPE(): Nothing = raiseError(ObjNullPointerError(this))
+    fun raiseNPE(): Nothing = raiseError(ObjNullPointerException(this))
 
     @Suppress("unused")
     fun raiseIndexOutOfBounds(message: String = "Index out of bounds"): Nothing =
-        raiseError(ObjIndexOutOfBoundsError(this, message))
+        raiseError(ObjIndexOutOfBoundsException(this, message))
 
     @Suppress("unused")
     fun raiseArgumentError(message: String = "Illegal argument error"): Nothing =
-        raiseError(ObjIllegalArgumentError(this, message))
+        raiseError(ObjIllegalArgumentException(this, message))
 
-    fun raiseClassCastError(msg: String): Nothing = raiseError(ObjClassCastError(this, msg))
+    fun raiseClassCastError(msg: String): Nothing = raiseError(ObjClassCastException(this, msg))
 
     @Suppress("unused")
     fun raiseSymbolNotFound(name: String): Nothing =
-        raiseError(ObjSymbolNotDefinedError(this, "symbol is not defined: $name"))
+        raiseError(ObjSymbolNotDefinedException(this, "symbol is not defined: $name"))
 
     fun raiseError(message: String): Nothing {
-        throw ExecutionError(ObjError(this, message))
+        throw ExecutionError(ObjException(this, message))
     }
 
-    fun raiseError(obj: ObjError): Nothing {
+    fun raiseError(obj: ObjException): Nothing {
         throw ExecutionError(obj)
     }
 

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

@@ -4,7 +4,10 @@ import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import net.sergeych.bintools.encodeToHex
 import net.sergeych.synctools.ProtectedOp
+import net.sergeych.synctools.withLock
+import kotlin.contracts.ExperimentalContracts
 
 /**
  * Record to store object with access rules, e.g. [isMutable] and access level [visibility].
@@ -63,7 +66,7 @@ open class Obj {
     suspend fun invokeInstanceMethod(context: Context, name: String, vararg args: Obj): Obj =
         invokeInstanceMethod(context, name, Arguments(args.toList()))
 
-    inline suspend fun <reified T : Obj> callMethod(
+    suspend inline fun <reified T : Obj> callMethod(
         context: Context,
         name: String,
         args: Arguments = Arguments.EMPTY
@@ -179,11 +182,10 @@ open class Obj {
 
     suspend fun <T> sync(block: () -> T): T = monitor.withLock { block() }
 
-    suspend open fun readField(context: Context, name: String): ObjRecord {
+    open suspend fun readField(context: Context, name: String): ObjRecord {
         // could be property or class field:
         val obj = objClass.getInstanceMemberOrNull(name) ?: context.raiseError("no such field: $name")
-        val value = obj.value
-        return when (value) {
+        return when (val value = obj.value) {
             is Statement -> {
                 ObjRecord(value.execute(context.copy(context.pos, newThisObj = this)), obj.isMutable)
             }
@@ -327,21 +329,100 @@ data class ObjNamespace(val name: String) : Obj() {
     }
 }
 
-open class ObjError(val context: Context, val message: String) : Obj() {
-    override val asStr: ObjString by lazy { ObjString("Error: $message") }
+open class ObjException(exceptionClass: ExceptionClass, val context: Context, val message: String) : Obj() {
+    constructor(name: String,context: Context, message: String) : this(getOrCreateExceptionClass(name), context, message)
+    constructor(context: Context, message: String) : this(Root, context, message)
 
     fun raise(): Nothing {
         throw ExecutionError(this)
     }
+
+    override val objClass: ObjClass = exceptionClass
+
+    override fun toString(): String {
+        return "ObjException:${objClass.className}:${context.pos}@${hashCode().encodeToHex()}"
     }
 
-class ObjNullPointerError(context: Context) : ObjError(context, "object is null")
+    companion object {
 
-class ObjAssertionError(context: Context, message: String) : ObjError(context, message)
-class ObjClassCastError(context: Context, message: String) : ObjError(context, message)
-class ObjIndexOutOfBoundsError(context: Context, message: String = "index out of bounds") : ObjError(context, message)
-class ObjIllegalArgumentError(context: Context, message: String = "illegal argument") : ObjError(context, message)
-class ObjIllegalAssignmentError(context: Context, message: String = "illegal assignment") : ObjError(context, message)
-class ObjSymbolNotDefinedError(context: Context, message: String = "symbol is not defined") : ObjError(context, message)
-class ObjIterationFinishedError(context: Context) : ObjError(context, "iteration finished")
-class ObjAccessError(context: Context, message: String = "access not allowed error") : ObjError(context, message)
+        class ExceptionClass(val name: String,vararg parents: ObjClass) : ObjClass(name, *parents) {
+            override suspend fun callOn(context: Context): Obj {
+                val message = context.args.getOrNull(0)?.toString() ?: name
+                return ObjException(this, context, message)
+            }
+            override fun toString(): String = "ExceptionClass[$name]@${hashCode().encodeToHex()}"
+        }
+        val Root = ExceptionClass("Throwable").apply {
+            addConst("message", statement {
+                (thisObj as ObjException).message.toObj()
+            })
+        }
+
+        private val op = ProtectedOp()
+        private val existingErrorClasses = mutableMapOf<String, ExceptionClass>()
+
+
+        @OptIn(ExperimentalContracts::class)
+        protected fun getOrCreateExceptionClass(name: String): ExceptionClass {
+            return op.withLock {
+                existingErrorClasses.getOrPut(name) {
+                    ExceptionClass(name, Root)
+                }
+            }
+        }
+
+        /**
+         * Get [ObjClass] for error class by name if exists.
+         */
+        @OptIn(ExperimentalContracts::class)
+        fun getErrorClass(name: String): ObjClass? = op.withLock {
+            existingErrorClasses[name]
+        }
+
+        fun addExceptionsToContext(context: Context) {
+            context.addConst("Exception", Root)
+            existingErrorClasses["Exception"] = Root
+            for (name in listOf(
+                "NullPointerException",
+                "AssertionFailedException",
+                "ClassCastException",
+                "IndexOutOfBoundsException",
+                "IllegalArgumentException",
+                "IllegalAssignmentException",
+                "SymbolNotDefinedException",
+                "IterationEndException",
+                "AccessException",
+                "UnknownException",
+            )) {
+                context.addConst(name, getOrCreateExceptionClass(name))
+            }
+        }
+    }
+}
+
+class ObjNullPointerException(context: Context) : ObjException("NullPointerException", context, "object is null")
+
+class ObjAssertionFailedException(context: Context, message: String) :
+    ObjException("AssertionFailedException", context, message)
+
+class ObjClassCastException(context: Context, message: String) : ObjException("ClassCastException", context, message)
+class ObjIndexOutOfBoundsException(context: Context, message: String = "index out of bounds") :
+    ObjException("IndexOutOfBoundsException", context, message)
+
+class ObjIllegalArgumentException(context: Context, message: String = "illegal argument") :
+    ObjException("IllegalArgumentException", context, message)
+
+class ObjIllegalAssignmentException(context: Context, message: String = "illegal assignment") :
+    ObjException("IllegalAssignmentException", context, message)
+
+class ObjSymbolNotDefinedException(context: Context, message: String = "symbol is not defined") :
+    ObjException("SymbolNotDefinedException", context, message)
+
+class ObjIterationFinishedException(context: Context) :
+    ObjException("IterationEndException", context, "iteration finished")
+
+class ObjAccessException(context: Context, message: String = "access not allowed error") :
+    ObjException("AccessException", context, message)
+
+class ObjUnknownException(context: Context, message: String = "access not allowed error") :
+    ObjException("UnknownException", context, message)

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

@@ -2,7 +2,7 @@ package net.sergeych.lyng
 
 val ObjClassType by lazy { ObjClass("Class") }
 
-class ObjClass(
+open class ObjClass(
     val className: String,
     vararg val parents: ObjClass,
 ) : Obj() {
@@ -122,7 +122,7 @@ class ObjArrayIterator(val array: Obj) : Obj() {
                     val self = thisAs<ObjArrayIterator>()
                     if (self.nextIndex < self.lastIndex) {
                         self.array.invokeInstanceMethod(this, "getAt", (self.nextIndex++).toObj())
-                    } else raiseError(ObjIterationFinishedError(this))
+                    } else raiseError(ObjIterationFinishedException(this))
                 }
                 addFn("hasNext") {
                     val self = thisAs<ObjArrayIterator>()

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

@@ -9,7 +9,7 @@ class ObjInstance(override val objClass: ObjClass) : Obj() {
             if (it.visibility.isPublic)
                 it
             else
-                context.raiseError(ObjAccessError(context, "can't access non-public field $name"))
+                context.raiseError(ObjAccessException(context, "can't access non-public field $name"))
         }
             ?: super.readField(context, name)
     }
@@ -17,8 +17,8 @@ class ObjInstance(override val objClass: ObjClass) : Obj() {
     override suspend fun writeField(context: Context, name: String, newValue: Obj) {
         instanceContext[name]?.let { f ->
             if (!f.visibility.isPublic)
-                ObjIllegalAssignmentError(context, "can't assign to non-public field $name")
-            if (!f.isMutable) ObjIllegalAssignmentError(context, "can't reassign val $name").raise()
+                ObjIllegalAssignmentException(context, "can't assign to non-public field $name")
+            if (!f.isMutable) ObjIllegalAssignmentException(context, "can't reassign val $name").raise()
             if (f.value.assign(context, newValue) == null)
                 f.value = newValue
         } ?: super.writeField(context, name, newValue)
@@ -29,7 +29,7 @@ class ObjInstance(override val objClass: ObjClass) : Obj() {
             if (it.visibility.isPublic)
                 it.value.invoke(context, this, args)
             else
-                context.raiseError(ObjAccessError(context, "can't invoke non-public method $name"))
+                context.raiseError(ObjAccessException(context, "can't invoke non-public method $name"))
         }
             ?: super.invokeInstanceMethod(context, name, args)
 

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

@@ -33,7 +33,7 @@ class ObjRangeIterator(val self: ObjRange) : Obj() {
             if( isCharRange ) ObjChar(x.toInt().toChar()) else ObjInt(x)
         }
         else {
-            context.raiseError(ObjIterationFinishedError(context))
+            context.raiseError(ObjIterationFinishedException(context))
         }
 
     companion object {

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

@@ -21,6 +21,7 @@ class Script(
 
     companion object {
         val defaultContext: Context = Context().apply {
+            ObjException.addExceptionsToContext(this)
             addFn("println") {
                 for ((i, a) in args.withIndex()) {
                     if (i > 0) print(' ' + a.asStr.value)
@@ -117,14 +118,14 @@ class Script(
             addVoidFn("assert") {
                 val cond = requiredArg<ObjBool>(0)
                 if( !cond.value == true )
-                    raiseError(ObjAssertionError(this,"Assertion failed"))
+                    raiseError(ObjAssertionFailedException(this,"Assertion failed"))
             }
 
             addVoidFn("assertEquals") {
                 val a = requiredArg<Obj>(0)
                 val b = requiredArg<Obj>(1)
                 if( a.compareTo(this, b) != 0 )
-                    raiseError(ObjAssertionError(this,"Assertion failed: ${a.inspect()} == ${b.inspect()}"))
+                    raiseError(ObjAssertionFailedException(this,"Assertion failed: ${a.inspect()} == ${b.inspect()}"))
             }
             addFn("assertThrows") {
                 val code = requireOnlyArg<Statement>()
@@ -138,7 +139,7 @@ class Script(
                 catch (e: ScriptError) {
                     ObjNull
                 }
-                result ?: raiseError(ObjAssertionError(this,"Expected exception but nothing was thrown"))
+                result ?: raiseError(ObjAssertionFailedException(this,"Expected exception but nothing was thrown"))
             }
 
             addVoidFn("delay") {

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

@@ -12,4 +12,4 @@ open class ScriptError(val pos: Pos, val errorMessage: String,cause: Throwable?=
     cause
 )
 
-class ExecutionError(val errorObject: ObjError) : ScriptError(errorObject.context.pos, errorObject.message)
+class ExecutionError(val errorObject: ObjException) : ScriptError(errorObject.context.pos, errorObject.message)

library/src/commonTest/kotlin/ScriptTest.kt

@@ -436,12 +436,14 @@ class ScriptTest {
 
     @Test
     fun whileAssignTest() = runTest {
-        eval("""
+        eval(
+            """
             var t = 0
             val x = while( t < 5 ) { t++ }
             // last returned value is 4 - when t was 5 body was not executed
             assertEquals( 4, x )
-        """.trimIndent())
+        """.trimIndent()
+        )
     }
 
     @Test
@@ -1597,32 +1599,37 @@ class ScriptTest {
 
     @Test
     fun testCallLastBlockAfterDetault() = runTest {
-        eval("""
+        eval(
+            """
             // this means last is lambda:
             fun f(e=1, f) {
                 "e="+e+"f="+f()
             }
             assertEquals("e=1f=xx", f { "xx" })
-        """.trimIndent())
+        """.trimIndent()
+        )
 
     }
 
     @Test
     fun testCallLastBlockWithEllipsis() = runTest {
-        eval("""
+        eval(
+            """
             // this means last is lambda:
             fun f(e..., f) {
                 "e="+e+"f="+f()
             }
             assertEquals("e=[]f=xx", f { "xx" })
             assertEquals("e=[1, 2]f=xx", f(1,2) { "xx" })
-        """.trimIndent())
+        """.trimIndent()
+        )
 
     }
 
     @Test
     fun testMethodCallLastBlockAfterDefault() = runTest {
-        eval("""
+        eval(
+            """
             class Foo {
                 // this means last is lambda:
                 fun f(e=1, f) {
@@ -1631,13 +1638,15 @@ class ScriptTest {
             }
             val f = Foo()
             assertEquals("e=1f=xx", f.f { "xx" })
-        """.trimIndent())
+        """.trimIndent()
+        )
 
     }
 
     @Test
     fun testMethodCallLastBlockWithEllipsis() = runTest {
-        eval("""
+        eval(
+            """
             class Foo {
                 // this means last is lambda:
                 fun f(e..., f) {
@@ -1647,13 +1656,15 @@ class ScriptTest {
             val f = Foo()
             assertEquals("e=[]f=xx", f.f { "xx" })
             assertEquals("e=[1, 2]f=xx", f.f(1,2) { "xx" })
-        """.trimIndent())
+        """.trimIndent()
+        )
 
     }
 
     @Test
     fun nationalCharsTest() = runTest {
-        eval("""
+        eval(
+            """
             fun сумма_ряда(x, погрешность=0.0001, f) {
                 var сумма = 0
                 for( n in 1..100000) {
@@ -1669,30 +1680,156 @@ class ScriptTest {
                 sign * pow(x, n) / n
             }
             assert( x - ln(2) < 0.001 )
-        """.trimIndent())
+        """.trimIndent()
+        )
     }
 
     @Test
     fun doWhileSimpleTest() = runTest {
-        eval("""
+        eval(
+            """
             var sum = 0
             var x = do {
                 val s = sum
                 sum += 1
             } while( s < 10 )
             assertEquals(11, x)
-        """.trimIndent())
+        """.trimIndent()
+        )
     }
 
     @Test
     fun testFailDoWhileSample1() = runTest {
-        eval("""
+        eval(
+            """
             fun readLine() { "done: result" }
             val result = do {
                 val line = readLine()
             } while( !line.startsWith("done:") )
             assertEquals("result", result.drop(6))
             result
+        """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testForContinue() = runTest {
+        eval(
+            """
+            var x = 0
+            for( i in 1..10 ) {
+                if( i % 2 == 0 ) continue
+                println(i)
+                x++
+            }
+            assertEquals(5, x)
+        """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testForLabelNreakTest() = runTest {
+        eval(
+            """
+            var x = 0
+            var y = 0
+            FOR0@ for( i in 1..10 ) {
+                x = i
+                for( j in 1..20 ) {
+                    y = j
+                    if( i == 3 && j == 5 ) {
+                        println("bb")
+                        break@FOR0
+                    }
+                }
+            }
+            assertEquals( 5, y )
+            assertEquals( 3, x )
+        """
+        )
+    }
+
+    @Test
+    fun testThrowExisting()= runTest {
+        eval("""
+            val x = IllegalArgumentException("test")
+            assert( x is Exception )
+
+            var t = 0
+            var finallyCaught = false
+            try {
+                t = 1
+                throw x
+                t = 2
+            }
+            catch( e: SymbolNotDefinedException ) {
+                t = 101
+            }
+            catch( e: IllegalArgumentException ) {
+                t = 3
+            }
+            finally {
+                finallyCaught = true
+            }
+            assertEquals(3, t)
+            assert(finallyCaught)
+        """.trimIndent())
+    }
+
+    @Test
+    fun testCatchShort1()= runTest {
+        eval("""
+            val x = IllegalArgumentException("test")
+            var t = 0
+            var finallyCaught = false
+            try {
+                t = 1
+                throw x
+                t = 2
+            }
+            catch(e) {
+                t = 31
+            }
+            finally {
+                finallyCaught = true
+            }
+            assertEquals(31, t)
+            assert(finallyCaught)
+        """.trimIndent())
+    }
+
+    @Test
+    fun testCatchShort2()= runTest {
+        eval("""
+            val x = IllegalArgumentException("test")
+            var caught = null
+            try {
+                throw x
+            }
+            catch {
+                caught = it
+            }
+            assert( caught is IllegalArgumentException )
+        """.trimIndent())
+    }
+
+    @Test
+    fun testAccessEHData() = runTest {
+        eval("""
+            val x = IllegalArgumentException("test")
+            val m = try {
+                throw x
+                null
+            }
+            catch(e) {
+                println(e)
+                println(e::class)
+                println(e.message)
+                println("--------------")
+                e.message    
+            }
+            println(m)
+            assert( m == "test" )
             """.trimIndent())
     }
 

library/src/jvmTest/kotlin/BookTest.kt

@@ -268,4 +268,9 @@ class BookTest {
     fun testArgumentBooks() = runTest {
         runDocTests("../docs/declaring_arguments.md")
     }
+
+    @Test
+    fun testExceptionsBooks() = runTest {
+        runDocTests("../docs/exceptions_handling.md")
+    }
 }