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Encapsulate scope into EvalContext;

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Fix bug with custom syntax delta.
This commit is contained in:
Stephen Chung
2020-10-19 19:11:55 +08:00
parent d1f9f4096d
commit a9fd0ff4de
15 changed files with 138 additions and 108 deletions
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38
doc/src/engine/custom-syntax.md
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@@ -114,25 +114,19 @@ Any custom syntax must include an _implementation_ of it.
The function signature of an implementation is:
> `Fn(scope: &mut Scope, context: &mut EvalContext, inputs: &[Expression])`
> `-> Result<Dynamic, Box<EvalAltResult>>`
> `Fn(context: &mut EvalContext, inputs: &[Expression]) -> Result<Dynamic, Box<EvalAltResult>>`
where:
* `scope: &mut Scope` - mutable reference to the current [`Scope`]; variables can be added to it.
* `context: &mut EvalContext` - mutable reference to the current evaluation _context_ (**do not touch**) which exposes the following fields:
* `context: &mut EvalContext` - mutable reference to the current evaluation _context_, exposing the following:
* `context.scope: &mut Scope` - mutable reference to the current [`Scope`]; variables can be added to/removed from it.
* `context.engine(): &Engine` - reference to the current [`Engine`].
* `context.namespace(): &Module` - reference to the current _global namespace_ (as a [module]) containing all script-defined functions.
* `context.this_ptr(): Option<&Dynamic>` - reference to the current bound [`this`] pointer, if any.
* `context.call_level(): usize` - the current nesting level of function calls.
* `inputs: &[Expression]` - a list of input expression trees.
#### WARNING - Lark's Vomit
The `context` parameter contains the evaluation _context_ and should not be touched or Bad Things Happen™.
It should simply be passed straight-through the the [`Engine`].
### Access Arguments
The most important argument is `inputs` where the matched identifiers (`$ident$`), expressions/statements (`$expr$`)
@@ -152,8 +146,8 @@ Use the `EvalContext::eval_expression_tree` method to evaluate an arbitrary expr
within the current evaluation context.
```rust
let expr = inputs.get(0).unwrap();
let result = context.eval_expression_tree(scope, expr)?;
let expression = inputs.get(0).unwrap();
let result = context.eval_expression_tree(expression)?;
```
### Declare Variables
@@ -163,15 +157,16 @@ New variables maybe declared (usually with a variable name that is passed in via
It can simply be pushed into the [`Scope`].
However, beware that all new variables must be declared _prior_ to evaluating any expression tree.
In other words, any `Scope::push` calls must come _before_ any `EvalContext::eval_expression_tree` calls.
In other words, any [`Scope`] calls that change the list of must come _before_ any
`EvalContext::eval_expression_tree` calls.
```rust
let var_name = inputs[0].get_variable_name().unwrap().to_string();
let expr = inputs.get(1).unwrap();
let var_name = inputs[0].get_variable_name().unwrap();
let expression = inputs.get(1).unwrap();
scope.push(var_name, 0 as INT); // do this BEFORE 'context.eval_expression_tree'!
context.scope.push(var_name, 0 as INT); // do this BEFORE 'context.eval_expression_tree'!
let result = context.eval_expression_tree(context, scope, expr)?;
let result = context.eval_expression_tree(expression)?;
```
@@ -188,7 +183,6 @@ The syntax is passed simply as a slice of `&str`.
```rust
// Custom syntax implementation
fn implementation_func(
scope: &mut Scope,
context: &mut EvalContext,
inputs: &[Expression]
) -> Result<Dynamic, Box<EvalAltResult>> {
@@ -196,15 +190,15 @@ fn implementation_func(
let stmt = inputs.get(1).unwrap();
let condition = inputs.get(2).unwrap();
// Push one new variable into the 'scope' BEFORE 'context.eval_expression_tree'
scope.push(var_name, 0 as INT);
// Push one new variable into the scope BEFORE 'context.eval_expression_tree'
context.scope.push(var_name, 0 as INT);
loop {
// Evaluate the statement block
context.eval_expression_tree(scope, stmt)?;
context.eval_expression_tree(stmt)?;
// Evaluate the condition expression
let stop = !context.eval_expression_tree(scope, condition)?
let stop = !context.eval_expression_tree(condition)?
.as_bool().map_err(|err| Box::new(
EvalAltResult::ErrorMismatchDataType(
"bool".to_string(),

6
doc/src/engine/var.md
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@@ -62,7 +62,7 @@ Function Signature
The function signature passed to `Engine::on_var` takes the following form:
> `Fn(name: &str, index: usize, scope: &Scope, context: &EvalContext)`
> `Fn(name: &str, index: usize, context: &EvalContext)`
> `-> Result<Option<Dynamic>, Box<EvalAltResult>> + 'static`
where:
@@ -74,11 +74,11 @@ where:
If `index` is zero, then there is no pre-calculated offset position and a search through the current [`Scope`] must be performed.
* `scope: &Scope` - reference to the current [`Scope`] containing all variables up to the current evaluation position.
* `context: &EvalContext` - reference to the current evaluation _context_, which exposes the following fields:
* `context.scope: &Scope` - reference to the current [`Scope`] containing all variables up to the current evaluation position.
* `context.engine(): &Engine` - reference to the current [`Engine`].
* `context.namespace(): &Module` - reference to the current _global namespace_ (as a [module]) containing all script-defined functions.
* `context.this_ptr(): Option<&Dynamic>` - reference to the current bound [`this`] pointer, if any.
* `context.call_level(): usize` - the current nesting level of function calls.
### Return Value