Refine code and docs.

This commit is contained in:
Stephen Chung
2020-11-03 21:50:14 +08:00
parent f74d947c6b
commit 32f41c69bd
11 changed files with 67 additions and 57 deletions

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@@ -24,7 +24,21 @@ engine.on_progress(|&count| { // parameter is '&u64' - number of operations al
The closure passed to `Engine::on_progress` will be called once for every operation.
Return `Some(token)` to terminate the script immediately, with the provided value
(any [`Dynamic`] value) passed to `EvalAltResult::ErrorTerminated` as a termination token.
(any [`Dynamic`]) acting as a termination token.
Termination Token
-----------------
The [`Dynamic`] value returned by the closure for `Engine::on_progress` is a _termination token_.
A script that is manually terminated returns with `Err(EvalAltResult::ErrorTerminated)`
wrapping this value.
The termination token is commonly used to provide information on the _reason_ or _source_
behind the termination decision.
If the termination token is not needed, simply return `Some(().into())` to terminate the script
run with [`()`] as the token.
Operations Count vs. Progress Percentage

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@@ -29,8 +29,9 @@ due to 64-bit arithmetic requiring more CPU cycles to complete.
Minimize Size of `Dynamic`
-------------------------
Turning on [`no_float`] and [`only_i32`] on 32-bit targets makes the critical [`Dynamic`] data type only 8 bytes long.
Normally [`Dynamic`] can be up to 16 bytes (e.g. on x86/x64 CPU's) in order to hold an `i64` or `f64`.
Turning on [`no_float`] or [`f32_float`] and [`only_i32`] on 32-bit targets makes the critical [`Dynamic`]
data type only 8 bytes long.
Normally [`Dynamic`] can be up to 12-16 bytes in order to hold an `i64` or `f64`.
A small [`Dynamic`] helps performance due to better cache efficiency.

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@@ -42,13 +42,14 @@ are typically used for a WASM build:
| Feature | Description |
| :-----------: | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`unchecked`] | When a WASM module panics, it doesn't crash the entire web app; however this also disables [maximum number of operations] and [progress] tracking so a script can still run indefinitely - the web app must terminate it itself. |
| [`only_i32`] | JavaScript has only one `number` type and we're only supporting `wasm32` here (so far). |
| [`only_i32`] | WASM supports 32-bit and 64-bit integers, but most scripts will only need 32-bit. |
| [`f32_float`] | WASM supports 32-bit single-precision and 64-bit double-precision floating-point numbers, but single-precision is usually fine for most uses. |
| [`no_module`] | A WASM module cannot load modules from the file system, so usually this is not needed, but the savings are minimal; alternatively, a custom [module resolver] can be provided that loads other Rhai scripts. |
The following features are typically _not_ used because they don't make sense in a WASM build:
| Feature | Why unnecessary |
| :-----------: | ------------------------------------------------------------------ |
| [`sync`] | WASM is single-threaded. |
| [`no_std`] | `std` lib works fine with WASM. |
| [`internals`] | WASM usually doesn't need to access Rhai internal data structures. |
| Feature | Why unnecessary |
| :-----------: | ------------------------------------------------------------------------------------------------------ |
| [`sync`] | WASM is single-threaded. |
| [`no_std`] | `std` lib works fine with WASM. |
| [`internals`] | WASM usually doesn't need to access Rhai internal data structures, unless you are walking the [`AST`]. |

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@@ -17,7 +17,7 @@ more control over what a script can (or cannot) do.
| `sync` | no | restricts all values types to those that are `Send + Sync`. Under this feature, all Rhai types, including [`Engine`], [`Scope`] and [`AST`], are all `Send + Sync` |
| `no_optimize` | no | disables [script optimization] |
| `no_float` | no | disables floating-point numbers and math |
| `f32_float` | no | sets the system floating-point type to `f32` instead of `f64` |
| `f32_float` | no | sets the system floating-point type to `f32` instead of `f64`. `FLOAT` is set to `f32` |
| `only_i32` | no | sets the system integer type to `i32` and disable all other integer types. `INT` is set to `i32` |
| `only_i64` | no | sets the system integer type to `i64` and disable all other integer types. `INT` is set to `i64` |
| `no_index` | no | disables [arrays] and indexing features |