+fn definitions and calls, closures

library/src/commonMain/kotlin/net/sergeych/ling/Arguments.kt

@@ -1,17 +1,19 @@
 package net.sergeych.ling
 
-data class Arguments(val list: List<Obj> ) {
+data class Arguments(val callerPos: Pos,val list: List<Info>) {
+
+    data class Info(val value: Obj,val pos: Pos)
 
     val size by list::size
 
-    operator fun get(index: Int): Obj = list[index]
+    operator fun get(index: Int): Obj = list[index].value
 
     fun firstAndOnly(): Obj {
         if( list.size != 1 ) throw IllegalArgumentException("Expected one argument, got ${list.size}")
-        return list.first()
+        return list.first().value
     }
 
     companion object {
-        val EMPTY = Arguments(emptyList())
+        val EMPTY = Arguments("".toSource().startPos,emptyList())
     }
 }

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

@@ -48,10 +48,10 @@ type alias has target type name. So we have to have something that denotes a _ty
 class Compiler {
 
     fun compile(source: Source): Script {
-        val tokens = parseLing(source).listIterator()
-        val start = source.startPos
-        // at this level: "global" context: just script to execute or new function
-        // declaration forming closures
+        return parseScript(source.startPos, parseLing(source).listIterator())
+    }
+
+    private fun parseScript(start: Pos, tokens: ListIterator<Token>): Script {
         val statements = mutableListOf<Statement>()
         while (parseStatement(tokens)?.also {
                 statements += it
@@ -90,6 +90,11 @@ class Compiler {
 
                 Token.Type.SEMICOLON -> continue
 
+                Token.Type.RBRACE -> {
+                    tokens.previous()
+                    return null
+                }
+
                 Token.Type.EOF -> null
 
                 else -> {
@@ -185,33 +190,44 @@ class Compiler {
                 val t = tokens.next()
                 if (t.type == Token.Type.ID) {
                     parseVarAccess(t, tokens, path + id.value)
-                }
-                else
+                } else
                     throw ScriptError(t.pos, "Expected identifier after '.'")
             }
+
             Token.Type.LPAREN -> {
+                // function call
                 // Load arg list
-                val args = mutableListOf<Statement>()
+                val args = mutableListOf<Arguments.Info>()
                 do {
                     val t = tokens.next()
                     when (t.type) {
                         Token.Type.RPAREN, Token.Type.COMMA -> {}
                         else -> {
                             tokens.previous()
-                            parseExpression(tokens)?.let { args += it }
+                            parseExpression(tokens)?.let { args += Arguments.Info(it, t.pos) }
                                 ?: throw ScriptError(t.pos, "Expecting arguments list")
                         }
                     }
                 } while (t.type != Token.Type.RPAREN)
+
                 statement(id.pos) { context ->
                     val v = resolve(context).get(id.value) ?: throw ScriptError(id.pos, "Undefined variable: $id")
-                    (v.value as? Statement)?.execute(context.copy(Arguments(args.map { it.execute(context) })))
+                    (v.value as? Statement)?.execute(
+                        context.copy(
+                            Arguments(
+                                nt.pos,
+                                args.map { Arguments.Info((it.value as Statement).execute(context), it.pos) }
+                            )
+                        )
+                    )
                         ?: throw ScriptError(id.pos, "Variable $id is not callable ($id)")
                 }
             }
+
             Token.Type.LBRACKET -> {
                 TODO("indexing")
             }
+
             else -> {
                 // just access the var
                 tokens.previous()
@@ -247,13 +263,89 @@ class Compiler {
      * Parse keyword-starting statenment.
      * @return parsed statement or null if, for example. [id] is not among keywords
      */
-    private fun parseKeywordStatement(id: Token, tokens: ListIterator<Token>): Statement?
-    = when (id.value) {
+    private fun parseKeywordStatement(id: Token, tokens: ListIterator<Token>): Statement? = when (id.value) {
         "val" -> parseVarDeclaration(id.value, false, tokens)
         "var" -> parseVarDeclaration(id.value, true, tokens)
+        "fn", "fun" -> parseFunctionDeclaration(tokens)
         else -> null
     }
 
+    data class FnParamDef(
+        val name: String,
+        val pos: Pos,
+        val defaultValue: Statement? = null
+    )
+
+    private fun parseFunctionDeclaration(tokens: ListIterator<Token>): Statement {
+        var t = tokens.next()
+        val start = t.pos
+        val name = if (t.type != Token.Type.ID)
+            throw ScriptError(t.pos, "Expected identifier after 'fn'")
+        else t.value
+
+        t = tokens.next()
+        if (t.type != Token.Type.LPAREN)
+            throw ScriptError(t.pos, "Bad function definition: expected '(' after 'fn ${name}'")
+        val params = mutableListOf<FnParamDef>()
+        var defaultListStarted = false
+        do {
+            t = tokens.next()
+            if (t.type == Token.Type.RPAREN)
+                break
+            if (t.type != Token.Type.ID)
+                throw ScriptError(t.pos, "Expected identifier after '('")
+            val n = tokens.next()
+            val defaultValue = if (n.type == Token.Type.ASSIGN) {
+                parseExpression(tokens)?.also { defaultListStarted = true }
+                    ?: throw ScriptError(n.pos, "Expected initialization expression")
+            } else {
+                if (defaultListStarted)
+                    throw ScriptError(n.pos, "requires default value too")
+                if (n.type != Token.Type.COMMA)
+                    tokens.previous()
+                null
+            }
+            params.add(FnParamDef(t.value, t.pos, defaultValue))
+        } while (true)
+
+        println("arglist: $params")
+
+        // Here we should be at open body
+        val fnStatements = parseBlock(tokens)
+
+        val fnBody = statement(t.pos) { context ->
+            // load params
+            for ((i, d) in params.withIndex()) {
+                if (i < context.args.size)
+                    context.addItem(d.name, false, context.args.list[i].value)
+                else
+                    context.addItem(
+                        d.name,
+                        false,
+                        d.defaultValue?.execute(context)
+                            ?: throw ScriptError(context.args.callerPos, "missing required argument #${1+i}: ${d.name}")
+                    )
+            }
+
+            fnStatements.execute(context)
+        }
+        return statement(start) { context ->
+            context.addItem(name, false, fnBody)
+            fnBody
+        }
+    }
+
+    private fun parseBlock(tokens: ListIterator<Token>): Statement {
+        val t = tokens.next()
+        if (t.type != Token.Type.LBRACE)
+            throw ScriptError(t.pos, "Expected block body start: {")
+        return parseScript(t.pos, tokens).also {
+            val t1 = tokens.next()
+            if (t1.type != Token.Type.RBRACE)
+                throw ScriptError(t1.pos, "unbalanced braces: expected block body end: }")
+        }
+    }
+
     private fun parseVarDeclaration(kind: String, mutable: Boolean, tokens: ListIterator<Token>): Statement {
         val nameToken = tokens.next()
         if (nameToken.type != Token.Type.ID)

library/src/commonMain/kotlin/net/sergeych/ling/Parser.kt

@@ -185,8 +185,4 @@ private class Parser(fromPos: Pos) {
     }
 
     private fun advance() = pos.advance()
-
-    init {
-//        advance()
-    }
 }

library/src/commonMain/kotlin/net/sergeych/ling/Pos.kt

@@ -39,8 +39,10 @@ class MutablePos(private val from: Pos) {
         return if (column+1 < current.length) {
             current[column++]
         } else {
-            line++
             column = 0
+            while( ++line < lines.size && lines[line].isEmpty() ) {
+                // skip empty lines
+            }
             if(line >= lines.size) null
             else lines[line][column]
         }
@@ -59,4 +61,7 @@ class MutablePos(private val from: Pos) {
 
     override fun toString() = "($line:$column)"
 
+    init {
+        if( lines[0].isEmpty()) advance()
+    }
 }

library/src/commonTest/kotlin/ScriptTest.kt

@@ -122,14 +122,45 @@ class ScriptTest {
         assertEquals(10, context.eval("b").toInt())
     }
 
-//    @Test
-//    fun functionTest() = runTest {
-//        val context = Context()
-//        context.eval("""
-//            fun foo(a, b) {
-//                a + b
-//            }
-//        """.trimIndent())
-//    }
+    @Test
+    fun functionTest() = runTest {
+        val context = Context()
+        context.eval(
+            """
+            fun foo(a, b) {
+                a + b
+            }
+        """.trimIndent()
+        )
+        assertEquals(17, context.eval("foo(3,14)").toInt())
+        assertFailsWith<ScriptError> {
+            assertEquals(17, context.eval("foo(3)").toInt())
+        }
+
+        context.eval("""
+            fn bar(a, b=10) {
+                a + b + 1
+            }
+        """.trimIndent())
+        assertEquals(10, context.eval("bar(3, 6)").toInt())
+        assertEquals(14, context.eval("bar(3)").toInt())
+    }
+
+    @Test
+    fun simpleClosureTest() = runTest {
+        val context = Context()
+        context.eval(
+            """
+            var global = 10
+            
+            fun foo(a, b) {
+                global + a + b
+            }
+        """.trimIndent()
+        )
+        assertEquals(27, context.eval("foo(3,14)").toInt())
+        context.eval("global = 20")
+        assertEquals(37, context.eval("foo(3,14)").toInt())
+    }
 
 }