gravlax - npm Package Compare versions

Comparing version 0.12.2 to 0.12.3

lib/main.js

 import { once } from "node:events";
 import * as fs from "node:fs/promises";
 import { createInterface } from "node:readline";
-import { Interpreter, stringify } from "./interpreter.js";
+import { Interpreter, RuntimeError, stringify } from "./interpreter.js";
 import { parse } from "./parser.js";
@@ -32,3 +32,11 @@ import { makeResolver } from "./resolver.js";
     if (expr) {
-      console.log(stringify(interpreter.evaluate(expr)));
+      try {
+        console.log(stringify(interpreter.evaluate(expr)));
+      } catch (e) {
+        if (e instanceof RuntimeError) {
+          runtimeError(e);
+        } else {
+          throw e;
+        }
+      }
     } else {
@@ -105,3 +113,3 @@ run(interpreter, line);
     console.error("Usage:", process.argv[1], "[script]");
-    process.exit(64);
+    return process.exit(64);
   }
@@ -108,0 +116,0 @@ const interpreter = new Interpreter();

package.json

 {
 	"name": "gravlax",
-	"version": "0.12.2",
+	"version": "0.12.3",
 	"description": "A Lox interpreter with tasty TypeScript seasoning",
@@ -5,0 +5,0 @@ "repository": {

README.md

@@ -27,2 +27,62 @@ <h1 align="center">Gravlax</h1>
 
+## Departures from the book
+
+### Features not in the book
+
+There's one notable feature I added beyond what's in the text of _Crafting Interpreters_: support for commas as numeric separators and currencies as first-class values.
+
+You can write `1,234 + 2,456` and gravlax will happily print out `3690`.
+Note that this has the… interesting side effect of making the grammar whitespace-sensitive:
+`f(1,2)` and `f(1, 2)` parse differently (the former is a one-argument call).
+
+You can also write out currency values like `$123` or `€456` and do math on them.
+The operations you'd expect to work will work: adding or subtracting values from the
+same currency is OK, multiply a currency by a scalar is OK, etc:
+
+```text
+> ($1,234 + $2,345) / 10
+$357.9
+> $12 + €23
+MixedCurrencyError: Operands must be the same currency.
+```
+
+Two other niceties:
+
+1. Support for expressions in the REPL ([Chapter 8 Challenge 1]).
+   If you run `npx gravlax` and then `1+2`, it will print `3`.
+   No need to write a `print` statement.
+   This makes it possible to use gravlax as a calculator.
+
+2. The REPL uses readline so you can hit up arrow to get the previous expression and edit it.
+
+### Implementation details
+
+Rather than representing AST nodes as classes, I used TypeScript `interface`s and
+a discriminated union for `Expr` and `Stmt`.
+This means that we don't need a codegen step.
+It also means that we [don't need the visitor pattern]:
+pattern-matching with `switch`/`case` is more idiomatic and less code.
+
+While I used a class for the Scanner (same as the book), I used a closure for the parser.
+Mostly this just means less writing `this` dot whatever.
+
+## Performance
+
+On my machine, gravlax runs the [Fibonacci code] from Chapter 14 in ~3 minutes (174 seconds).
+Compare this with 27s for jlox.
+So we're ~6x slower than Java.
+
+In jlox and gravlax, returning from a function is implemented by throwing an exception.
+It's critical that this class not derive from `Error`, so that it doesn't carry
+along stack traces:
+
+```text
+- class ReturnCall extends Error {
++ class ReturnCall {
+```
+
+The latter winds up being ~10x faster than the former.
+This is the JS equivalent of the [weird] `super(null, null, false, false)` call in jlox.
+See [#37].
+
 ## Development
@@ -63,1 +123,6 @@
 [Recurse Center]: https://www.recurse.com/
+[Chapter 8 Challenge 1]: https://craftinginterpreters.com/statements-and-state.html#challenges
+[don't need the visitor pattern]: https://github.com/danvk/gravlax/pull/35
+[Fibonacci code]: https://craftinginterpreters.com/chunks-of-bytecode.html
+[#37]: https://github.com/danvk/gravlax/pull/37
+[weird]: https://craftinginterpreters.com/functions.html

No alert changes

Improved metrics

Total package byte prevSize

144470

increased by2.16%

Lines of code

1564

increased by0.51%

Number of lines in readme file

127

increased by104.84%

No dependency changes