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Edit documentation.

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This commit is contained in:
Stephen Chung
2020-06-22 00:03:45 +08:00
parent 7cc1a3f5dc
commit d728ac6758
37 changed files with 386 additions and 147 deletions
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32
doc/src/language/eval.md
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@@ -6,29 +6,29 @@
Or "How to Shoot Yourself in the Foot even Easier"
------------------------------------------------
Saving the best for last: in addition to script optimizations, there is the ever-dreaded... `eval` function!
Saving the best for last, there is the ever-dreaded... `eval` function!
```rust
let x = 10;
fn foo(x) { x += 12; x }
let script = "let y = x;"; // build a script
let script = "let y = x;"; // build a script
script += "y += foo(y);";
script += "x + y";
let result = eval(script); // <- look, JS, we can also do this!
let result = eval(script); // <- look, JS, we can also do this!
print("Answer: " + result); // prints 42
print("Answer: " + result); // prints 42
print("x = " + x); // prints 10: functions call arguments are passed by value
print("y = " + y); // prints 32: variables defined in 'eval' persist!
print("x = " + x); // prints 10: functions call arguments are passed by value
print("y = " + y); // prints 32: variables defined in 'eval' persist!
eval("{ let z = y }"); // to keep a variable local, use a statement block
eval("{ let z = y }"); // to keep a variable local, use a statement block
print("z = " + z); // <- error: variable 'z' not found
print("z = " + z); // <- error: variable 'z' not found
"print(42)".eval(); // <- nope... method-call style doesn't work
"print(42)".eval(); // <- nope... method-call style doesn't work
```
Script segments passed to `eval` execute inside the current [`Scope`], so they can access and modify _everything_,
@@ -45,8 +45,8 @@ not inside another function call!
```rust
let script = "x += 32";
let x = 10;
eval(script); // variable 'x' in the current scope is visible!
print(x); // prints 42
eval(script); // variable 'x' in the current scope is visible!
print(x); // prints 42
// The above is equivalent to:
let script = "x += 32";
@@ -65,7 +65,7 @@ disable `eval` by overloading it, probably with something that throws.
```rust
fn eval(script) { throw "eval is evil! I refuse to run " + script }
let x = eval("40 + 2"); // 'eval' here throws "eval is evil! I refuse to run 40 + 2"
let x = eval("40 + 2"); // 'eval' here throws "eval is evil! I refuse to run 40 + 2"
```
Or overload it from Rust:
@@ -86,11 +86,11 @@ There is even a package named [`EvalPackage`]({{rootUrl}}/rust/packages.md) whic
```rust
use rhai::Engine;
use rhai::packages::Package // load the 'Package' trait to use packages
use rhai::packages::EvalPackage; // the 'eval' package disables 'eval'
use rhai::packages::Package // load the 'Package' trait to use packages
use rhai::packages::EvalPackage; // the 'eval' package disables 'eval'
let mut engine = Engine::new();
let package = EvalPackage::new(); // create the package
let package = EvalPackage::new(); // create the package
engine.load_package(package.get()); // load the package
engine.load_package(package.get()); // load the package
```