diff --git a/packages/parse/src/api.ts b/packages/parse/src/api.ts
index 02c56de696..61a6d5bfb4 100644
--- a/packages/parse/src/api.ts
+++ b/packages/parse/src/api.ts
@@ -3,7 +3,7 @@ import { ParseContext } from "./context";
 
 export interface ParseScope<T> {
     id: string;
-    state: ParseState<T>;
+    state: Nullable<ParseState<T>>;
     children: Nullable<ParseScope<T>[]>;
     result: any;
 }
diff --git a/packages/parse/src/context.ts b/packages/parse/src/context.ts
index 65d7709704..7f683976d5 100644
--- a/packages/parse/src/context.ts
+++ b/packages/parse/src/context.ts
@@ -1,6 +1,7 @@
+import { isString } from "@thi.ng/checks";
 import type { IReader, ParseScope } from "./api";
 import { parseError } from "./error";
-import { defStringReader } from "./string-reader";
+import { defStringReader } from "./readers/string-reader";
 
 interface ContextOpts {
     /**
@@ -10,24 +11,34 @@ interface ContextOpts {
      */
     maxDepth: number;
     /**
-     * True to enable parser debug output.
+     * True to enable parser debug output. Will emit details of each
+     * parse scope.
      *
      * @defaultValue false
      */
     debug: boolean;
+    /**
+     * True to retain reader state for each AST node. State of root node
+     * is always available.
+     *
+     * @defaultValue false
+     */
+    retain: boolean;
 }
 
 export class ParseContext<T> {
-    maxDepth: number;
-    debug: boolean;
-
     protected _scopes: ParseScope<T>[];
     protected _curr: ParseScope<T>;
 
+    protected _maxDepth: number;
+    protected _debug: boolean;
+    protected _retain: boolean;
+
     constructor(public reader: IReader<T>, opts?: Partial<ContextOpts>) {
-        opts = { maxDepth: 32, debug: false, ...opts };
-        this.maxDepth = opts.maxDepth!;
-        this.debug = opts.debug!;
+        opts = { maxDepth: 32, debug: false, retain: false, ...opts };
+        this._maxDepth = opts.maxDepth!;
+        this._debug = opts.debug!;
+        this._retain = opts.retain!;
         this._curr = {
             id: "root",
             state: { p: 0, l: 1, c: 1 },
@@ -35,24 +46,24 @@ export class ParseContext<T> {
             result: null,
         };
         this._scopes = [this._curr];
-        reader.isDone(this._curr.state);
+        reader.isDone(this._curr.state!);
     }
 
     start(id: string) {
-        if (this._scopes.length >= this.maxDepth) {
-            parseError(this, `recursion limit reached ${this.maxDepth}`);
+        if (this._scopes.length >= this._maxDepth) {
+            parseError(this, `recursion limit reached ${this._maxDepth}`);
         }
         const scopes = this._scopes;
         const scope: ParseScope<T> = {
             id,
-            state: { ...scopes[scopes.length - 1].state },
+            state: { ...scopes[scopes.length - 1].state! },
             children: null,
             result: null,
         };
         scopes.push(scope);
-        if (this.debug) {
+        if (this._debug) {
             console.log(
-                `${" ".repeat(scopes.length)}start: ${id} (${scope.state.p})`
+                `${" ".repeat(scopes.length)}start: ${id} (${scope.state!.p})`
             );
         }
         return (this._curr = scope);
@@ -62,7 +73,7 @@ export class ParseContext<T> {
         const scopes = this._scopes;
         const child = scopes.pop()!;
         this._curr = scopes[scopes.length - 1];
-        if (this.debug) {
+        if (this._debug) {
             console.log(`${" ".repeat(scopes.length + 1)}discard: ${child.id}`);
         }
         return false;
@@ -74,12 +85,16 @@ export class ParseContext<T> {
         const parent = scopes[scopes.length - 1];
         const cstate = child.state;
         const pstate = parent.state;
-        if (this.debug) {
+        if (this._debug) {
             console.log(
-                `${" ".repeat(scopes.length + 1)}end: ${child.id} (${cstate.p})`
+                `${" ".repeat(scopes.length + 1)}end: ${child.id} (${
+                    cstate!.p
+                })`
             );
         }
-        child.state = { p: pstate.p, l: pstate.l, c: pstate.c };
+        child.state = this._retain
+            ? { p: pstate!.p, l: pstate!.l, c: pstate!.c }
+            : null;
         parent.state = cstate;
         const children = parent.children;
         children ? children.push(child) : (parent.children = [child]);
@@ -92,7 +107,9 @@ export class ParseContext<T> {
         const cstate = curr.state;
         const child: ParseScope<T> = {
             id,
-            state: { p: cstate.p, l: cstate.l, c: cstate.c },
+            state: this._retain
+                ? { p: cstate!.p, l: cstate!.l, c: cstate!.c }
+                : null,
             children: null,
             result,
         };
@@ -110,7 +127,7 @@ export class ParseContext<T> {
     }
 
     get done() {
-        return this._curr.state.done;
+        return this._curr.state!.done;
     }
 
     /**
@@ -138,10 +155,26 @@ export class ParseContext<T> {
 }
 
 /**
- * Creates new {@link ParseContext} for given input string and context options.
+ * Creates new {@link ParseContext} for given input string or reader and
+ * context options.
  *
  * @param input -
  * @param opts -
  */
-export const defContext = (input: string, opts?: Partial<ContextOpts>) =>
-    new ParseContext<string>(defStringReader(input), opts);
+export function defContext(
+    input: string,
+    opts?: Partial<ContextOpts>
+): ParseContext<string>;
+export function defContext<T>(
+    input: IReader<T>,
+    opts?: Partial<ContextOpts>
+): ParseContext<T>;
+export function defContext(
+    input: string | IReader<any>,
+    opts?: Partial<ContextOpts>
+): ParseContext<any> {
+    return new ParseContext<string>(
+        isString(input) ? defStringReader(input) : input,
+        opts
+    );
+}
diff --git a/packages/parse/src/error.ts b/packages/parse/src/error.ts
index 44a39dcb1a..0fc7875635 100644
--- a/packages/parse/src/error.ts
+++ b/packages/parse/src/error.ts
@@ -4,6 +4,6 @@ import { ParseContext } from "./context";
 const ParseError = defError(() => `ParseError`);
 
 export const parseError = (ctx: ParseContext<any>, msg: string): never => {
-    const info = ctx.reader.format(ctx.scope.state);
+    const info = ctx.reader.format(ctx.scope.state!);
     throw new ParseError(msg + (info ? ` @ ${info}` : ""));
 };
diff --git a/packages/parse/src/prims/anchor.ts b/packages/parse/src/prims/anchor.ts
index 6714473b37..aae5cca3e3 100644
--- a/packages/parse/src/prims/anchor.ts
+++ b/packages/parse/src/prims/anchor.ts
@@ -4,21 +4,21 @@ import type { Parser } from "../api";
 export const anchor = <T>(
     fn: Fn2<Nullable<T>, Nullable<T>, boolean>
 ): Parser<T> => (ctx) => {
-    const state = ctx.state;
+    const state = ctx.state!;
     return fn(state.last, state.done ? null : ctx.reader.read(state));
 };
 
-export const inputStart: Parser<any> = (ctx) => ctx.state.last == null;
+export const inputStart: Parser<any> = (ctx) => ctx.state!.last == null;
 
 export const inputEnd: Parser<any> = (ctx) =>
-    ctx.state.done || !ctx.reader.read(ctx.state);
+    ctx.state!.done || !ctx.reader.read(ctx.state!);
 
 export const lineStart: Parser<string> = (ctx) => {
-    const l = ctx.state.last;
+    const l = ctx.state!.last;
     return l == null || l === "\n";
 };
 
 export const lineEnd: Parser<string> = (ctx) => {
-    const state = ctx.state;
+    const state = ctx.state!;
     return state.done || ctx.reader.read(state) === "\n";
 };
diff --git a/packages/parse/src/prims/range.ts b/packages/parse/src/prims/range.ts
index da5006aa08..b69665e244 100644
--- a/packages/parse/src/prims/range.ts
+++ b/packages/parse/src/prims/range.ts
@@ -3,3 +3,16 @@ import { satisfy } from "./satisfy";
 
 export const range = <T extends NumOrString>(min: T, max: T, id = "lit") =>
     satisfy<T>((x) => x >= min && x <= max, id);
+
+/**
+ * Matches single char in given UTF-16 code range.
+ *
+ * @param min
+ * @param max
+ * @param id
+ */
+export const utf16Range = (min: number, max: number, id = "utfLit") =>
+    satisfy<string>((x) => {
+        const c = x.charCodeAt(0)!;
+        return c >= min && c <= max;
+    }, id);
diff --git a/packages/parse/src/prims/satisfy.ts b/packages/parse/src/prims/satisfy.ts
index 1107380e63..54b16676ef 100644
--- a/packages/parse/src/prims/satisfy.ts
+++ b/packages/parse/src/prims/satisfy.ts
@@ -6,12 +6,12 @@ export const satisfy = <T>(fn: Predicate<T>, id = "lit"): Parser<T> => (
 ) => {
     if (ctx.done) return false;
     const reader = ctx.reader;
-    const r = reader.read(ctx.state);
+    const r = reader.read(ctx.state!);
     if (!fn(r)) {
         return false;
     }
     const scope = ctx.start(id);
-    reader.next(scope.state);
+    reader.next(scope.state!);
     scope.result = r;
     return ctx.end();
 };
diff --git a/packages/parse/src/prims/string.ts b/packages/parse/src/prims/string.ts
index 991ccd84d9..3c8a420629 100644
--- a/packages/parse/src/prims/string.ts
+++ b/packages/parse/src/prims/string.ts
@@ -5,7 +5,7 @@ export const string = <T>(str: ArrayLike<T>, id = "string"): Parser<T> => (
 ) => {
     if (ctx.done) return false;
     const scope = ctx.start(id);
-    const state = scope.state;
+    const state = scope.state!;
     const reader = ctx.reader;
     for (let i = 0, n = str.length; i < n; i++) {
         if (state.done) return false;
diff --git a/packages/parse/src/xform/print.ts b/packages/parse/src/xform/print.ts
index a18eea3583..0b93bc8bcf 100644
--- a/packages/parse/src/xform/print.ts
+++ b/packages/parse/src/xform/print.ts
@@ -3,11 +3,9 @@ import { ScopeTransform } from "../api";
 export const xfPrint: ScopeTransform<any> = (scope, _, indent = 0) => {
     if (!scope) return;
     const prefix = indent > 0 ? "  ".repeat(indent) : "";
-    console.log(
-        `${prefix}${scope.id} (${scope.state.l}:${
-            scope.state.c
-        }): ${JSON.stringify(scope.result)}`
-    );
+    const state = scope.state;
+    const info = state ? ` (${state.l}:${state.c})` : "";
+    console.log(`${prefix}${scope.id}${info}: ${JSON.stringify(scope.result)}`);
     if (scope.children) {
         for (let c of scope.children) {
             xfPrint(c, _, indent + 1);
diff --git a/packages/parse/test/index.ts b/packages/parse/test/index.ts
index 469762ba54..a889b806b4 100644
--- a/packages/parse/test/index.ts
+++ b/packages/parse/test/index.ts
@@ -17,7 +17,7 @@ const check = (
 ) => {
     const ctx = defContext(src);
     assert.equal(parser(ctx), res, `src: '${src}'`);
-    assert.equal(ctx.state.p, pos, `src: '${src}' pos: ${ctx.state.p}`);
+    assert.equal(ctx.state!.p, pos, `src: '${src}' pos: ${ctx.state!.p}`);
 };
 
 describe("parse", () => {
diff --git a/packages/parse/test/rpn.ts b/packages/parse/test/rpn.ts
index adcd207569..9ba4bcc4be 100644
--- a/packages/parse/test/rpn.ts
+++ b/packages/parse/test/rpn.ts
@@ -1,6 +1,6 @@
 import { Fn2 } from "@thi.ng/api";
 import * as assert from "assert";
-import { alt, defContext, INT, oneOf, WS, xform, zeroOrMore } from "../src";
+import { alt, defContext, FLOAT, oneOf, WS_0, xform, zeroOrMore } from "../src";
 
 describe("parse", () => {
     it("RPN calc", () => {
@@ -11,7 +11,7 @@ describe("parse", () => {
             "*": (a, b) => a * b,
             "/": (a, b) => a / b,
         };
-        const value = xform(INT, (scope) => {
+        const value = xform(FLOAT, (scope) => {
             stack.push(scope!.result);
             return null;
         });
@@ -21,7 +21,7 @@ describe("parse", () => {
             stack.push(ops[scope!.result](a, b));
             return null;
         });
-        const program = zeroOrMore(alt([value, op, zeroOrMore(WS)]));
+        const program = zeroOrMore(alt([value, op, WS_0]));
         const ctx = defContext("10 5 3 * + -2 * 10 /");
         assert(program(ctx));
         assert(ctx.done);
diff --git a/packages/parse/test/svg.ts b/packages/parse/test/svg.ts
index ff5a7fa4ab..52a78cd129 100644
--- a/packages/parse/test/svg.ts
+++ b/packages/parse/test/svg.ts
@@ -8,7 +8,7 @@ import {
     oneOf,
     Parser,
     seq,
-    WS,
+    WS_0,
     xform,
     zeroOrMore,
 } from "../src";
@@ -21,18 +21,17 @@ const check = (
 ) => {
     const ctx = defContext(src);
     assert.equal(parser(ctx), res, `src: '${src}'`);
-    assert.equal(ctx.state.p, pos, `src: '${src}' pos: ${ctx.state.p}`);
+    assert.equal(ctx.state!.p, pos, `src: '${src}' pos: ${ctx.state!.p}`);
 };
 
 describe("parse", () => {
     it("SVG", () => {
-        const ws = discard(zeroOrMore(WS));
         const wsc = discard(zeroOrMore(oneOf(" \n,")));
         const point = collect(seq([INT, wsc, INT]));
-        const move = collect(seq([oneOf("Mm"), ws, point, ws]));
-        const line = collect(seq([oneOf("Ll"), ws, point, ws]));
+        const move = collect(seq([oneOf("Mm"), WS_0, point, WS_0]));
+        const line = collect(seq([oneOf("Ll"), WS_0, point, WS_0]));
         const curve = collect(
-            seq([oneOf("Cc"), ws, point, wsc, point, wsc, point, ws])
+            seq([oneOf("Cc"), WS_0, point, wsc, point, wsc, point, WS_0])
         );
         const close = xform(oneOf("Zz"), ($) => (($!.result = [$!.result]), $));
         const path = collect(zeroOrMore(alt([move, line, curve, close])));