Add structural comparison

README.md

@@ -434,6 +434,10 @@ not the subset of ValueScript that has actually been implemented.
 - Iterators
 - Spread operator on iterables
 - Generators
+- Structural comparison (not yet for class instances)
+  - `{} === {} -> true`
+  - JS: `-> false`
+  - This is a value semantics thing - objects don't have identity
 - Many unusual JS things:
   - `[] + [] -> ""`
   - `[10, 1, 3].sort() -> [1, 10, 3]`
@@ -468,10 +472,7 @@ not the subset of ValueScript that has actually been implemented.
     - Uses `.toString()` to get the source code and compiles and runs it in
       WebAssembly
   - C libraries, and bindings for python etc
-- Structural comparison
-  - `{} === {} -> true`
-  - JS: `-> false`
-  - This is a value semantics thing - objects don't have identity
+- Comparison of class instances and functions
 - Object spreading
 - Rest params
 - Async functions

inputs/passing/structureCmp.ts

@@ -0,0 +1,39 @@
+//! test_output(24)
+
+export default function () {
+  let count = 0;
+
+  const cases: [unknown, unknown, { loose: boolean; strict: boolean }][] = [
+    [[], [], { loose: true, strict: true }],
+    [[], [1], { loose: false, strict: false }],
+    [[1, 2, 3], [1, 2, 3], { loose: true, strict: true }],
+    [[1, 2, 3], [1, "2", 3], { loose: true, strict: false }],
+    [{}, {}, { loose: true, strict: true }],
+    [{}, { x: 1 }, { loose: false, strict: false }],
+    [{}, { [Symbol.iterator]: 1 }, { loose: false, strict: false }],
+    [{ x: 1, y: 2, z: 3 }, { x: 1, y: 2, z: 3 }, { loose: true, strict: true }],
+    [{ x: 1, y: 2, z: 3 }, { x: 1, y: "2", z: 3 }, {
+      loose: true,
+      strict: false,
+    }],
+    [[[[[[1]]]]], [[[[[1]]]]], { loose: true, strict: true }],
+    [[[[[["1"]]]]], [[[[[1]]]]], { loose: true, strict: false }],
+    [null, undefined, { loose: true, strict: false }],
+  ];
+
+  for (const [left, right, { loose, strict }] of cases) {
+    if ((left == right) === loose) {
+      count++;
+    } else {
+      throw new Error(`Expected ${left} == ${right} to be ${loose}`);
+    }
+
+    if ((left === right) === strict) {
+      count++;
+    } else {
+      throw new Error(`Expected ${left} === ${right} to be ${strict}`);
+    }
+  }
+
+  return count;
+}

valuescript_vm/src/operations.rs

@@ -1,3 +1,4 @@
+use std::collections::BTreeMap;
 use std::mem::take;
 use std::rc::Rc;
 use std::str::FromStr;
@@ -124,8 +125,64 @@ pub fn op_eq_impl(left: &Val, right: &Val) -> Result<bool, Val> {
     (Val::Bool(left_bool), Val::Bool(right_bool)) => left_bool == right_bool,
     (Val::Number(left_number), Val::Number(right_number)) => left_number == right_number,
     (Val::String(left_string), Val::String(right_string)) => left_string == right_string,
+    (Val::Number(left_number), Val::String(right_string)) => {
+      left_number.to_string() == **right_string
+    }
+    (Val::String(left_string), Val::Number(right_number)) => {
+      **left_string == right_number.to_string()
+    }
     (Val::BigInt(left_bigint), Val::BigInt(right_bigint)) => left_bigint == right_bigint,
+    (Val::Array(left_array), Val::Array(right_array)) => 'b: {
+      if &**left_array as *const _ == &**right_array as *const _ {
+        break 'b true;
+      }
+
+      let len = left_array.elements.len();
+
+      if right_array.elements.len() != len {
+        break 'b false;
+      }
+
+      for (left_item, right_item) in left_array.elements.iter().zip(right_array.elements.iter()) {
+        if !op_eq_impl(left_item, right_item)? {
+          break 'b false;
+        }
+      }
+
+      true
+    }
+    (Val::Object(left_object), Val::Object(right_object)) => 'b: {
+      if left_object.prototype.is_some() || right_object.prototype.is_some() {
+        return Err("TODO: class instance comparison".to_internal_error());
+      }
+
+      if &**left_object as *const _ == &**right_object as *const _ {
+        break 'b true;
+      }
+
+      if !compare_btrees(
+        &left_object.string_map,
+        &right_object.string_map,
+        op_eq_impl,
+      )? {
+        break 'b false;
+      }
+
+      if !compare_btrees(
+        &left_object.symbol_map,
+        &right_object.symbol_map,
+        op_eq_impl,
+      )? {
+        break 'b false;
+      }
+
+      true
+    }
     _ => {
+      if left.is_truthy() != right.is_truthy() {
+        return Ok(false);
+      }
+
       return Err(
         format!(
           "TODO: op== with other types ({}, {})",
@@ -133,11 +190,34 @@ pub fn op_eq_impl(left: &Val, right: &Val) -> Result<bool, Val> {
           right.codify()
         )
         .to_internal_error(),
-      )
+      );
     }
   })
 }
 
+fn compare_btrees<K, Cmp>(
+  left: &BTreeMap<K, Val>,
+  right: &BTreeMap<K, Val>,
+  cmp: Cmp,
+) -> Result<bool, Val>
+where
+  Cmp: Fn(&Val, &Val) -> Result<bool, Val>,
+{
+  let symbol_len = left.len();
+
+  if right.len() != symbol_len {
+    return Ok(false);
+  }
+
+  for (left_value, right_value) in left.values().zip(right.values()) {
+    if !cmp(left_value, right_value)? {
+      return Ok(false);
+    }
+  }
+
+  Ok(true)
+}
+
 pub fn op_eq(left: &Val, right: &Val) -> Result<Val, Val> {
   Ok(Val::Bool(op_eq_impl(left, right)?))
 }
@@ -154,12 +234,65 @@ pub fn op_triple_eq_impl(left: &Val, right: &Val) -> Result<bool, Val> {
     (Val::Number(left_number), Val::Number(right_number)) => left_number == right_number,
     (Val::String(left_string), Val::String(right_string)) => left_string == right_string,
     (Val::BigInt(left_bigint), Val::BigInt(right_bigint)) => left_bigint == right_bigint,
-    _ => {
-      if left.typeof_() != right.typeof_() {
-        false
-      } else {
-        return Err("TODO: op=== with other types".to_internal_error());
+    (Val::Array(left_array), Val::Array(right_array)) => 'b: {
+      if &**left_array as *const _ == &**right_array as *const _ {
+        break 'b true;
       }
+
+      let len = left_array.elements.len();
+
+      if right_array.elements.len() != len {
+        break 'b false;
+      }
+
+      for (left_item, right_item) in left_array.elements.iter().zip(right_array.elements.iter()) {
+        if !op_triple_eq_impl(left_item, right_item)? {
+          break 'b false;
+        }
+      }
+
+      true
+    }
+    (Val::Object(left_object), Val::Object(right_object)) => 'b: {
+      if left_object.prototype.is_some() || right_object.prototype.is_some() {
+        return Err("TODO: class instance comparison".to_internal_error());
+      }
+
+      if &**left_object as *const _ == &**right_object as *const _ {
+        break 'b true;
+      }
+
+      if !compare_btrees(
+        &left_object.string_map,
+        &right_object.string_map,
+        op_triple_eq_impl,
+      )? {
+        break 'b false;
+      }
+
+      if !compare_btrees(
+        &left_object.symbol_map,
+        &right_object.symbol_map,
+        op_triple_eq_impl,
+      )? {
+        break 'b false;
+      }
+
+      true
+    }
+    (Val::Static(..) | Val::Dynamic(..) | Val::CopyCounter(..), _)
+    | (_, Val::Static(..) | Val::Dynamic(..) | Val::CopyCounter(..)) => {
+      if left.typeof_() != right.typeof_() {
+        return Ok(false);
+      }
+
+      return Err(
+        format!("TODO: op=== with special types ({}, {})", left, right).to_internal_error(),
+      );
+    }
+    _ => {
+      assert!(left.typeof_() != right.typeof_());
+      false
     }
   })
 }

website/src/playground/files/index.ts

@@ -11,6 +11,7 @@ export const orderedFiles = [
   "/tutorial/revertOnCatch.ts",
   "/tutorial/strings.ts",
   "/tutorial/const.ts",
+  "/tutorial/structuralComparison.ts",
   "/tutorial/binaryTree.ts",
   "/tutorial/specialFunctions.ts",
   "/tutorial/treeShaking.ts",

website/src/playground/files/root/tutorial/structuralComparison.ts

@@ -0,0 +1,22 @@
+// Also due to value semantics, arrays and objects are compared on their content instead of their
+// identity.
+
+export default function () {
+  return vec3(-5, 7, 12) === vec3(-5, 7, 12);
+  // JavaScript:  false
+  // ValueScript: true
+}
+
+function vec3(x: number, y: number, z: number) {
+  return { x, y, z };
+}
+
+// Caveat:
+// - TypeScript will emit an error for expressions like `[a, b] === [c, d]`.
+//
+// This is unfortunate. It's to protect you from accidentally expecting structural comparison in JS,
+// but in ValueScript, that's exactly how it *does* work.
+//
+// ValueScript will still happily evaluate these expressions (ValueScript doesn't use the TS
+// compiler), but you might want to rewrite these expressions as `eq([a, b], [c, d])` until
+// dedicated ValueScript intellisense is available.