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Refine docs.

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Stephen Chung
2020-09-19 12:14:02 +08:00
parent b795ce9f45
commit 2ff3a1fde5
18 changed files with 133 additions and 107 deletions
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doc/src/engine/dsl.md
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@@ -69,12 +69,12 @@ For example, the following is a SQL-like syntax for some obscure DSL operation:
```rust
let table = [..., ..., ..., ...];
// Syntax = calculate $ident$ $ident$ from $expr$ -> $ident$ : $expr$
let total = calculate sum price from table -> row : row.weight > 50;
// Syntax = calculate $ident$ ( $expr$ -> $ident$ ) => $ident$ : $expr$
let total = calculate sum(table->price) => row : row.weight > 50;
// Note: There is nothing special about those symbols; to make it look exactly like SQL:
// Syntax = SELECT $ident$ ( $ident$ ) FROM $expr$ AS $ident$ WHERE $expr$
let total = SELECT sum(price) FROM table AS row WHERE row.weight > 50;
// Syntax = SELECT $ident$ ( $ident$ ) AS $ident$ FROM $expr$ WHERE $expr$
let total = SELECT sum(price) AS row FROM table WHERE row.weight > 50;
```
After registering this custom syntax with Rhai, it can be used anywhere inside a script as
@@ -84,9 +84,9 @@ For its evaluation, the callback function will receive the following list of inp
* `inputs[0] = "sum"` - math operator
* `inputs[1] = "price"` - field name
* `inputs[2] = Expression(table)` - data source
* `inputs[3] = "row"` - loop variable name
* `inputs[2] = "row"` - loop variable name
* `inputs[3] = Expression(table)` - data source
* `inputs[4] = Expression(row.wright > 50)` - filter predicate
Other identifiers, such as `"calculate"`, `"from"`, as well as symbols such as `->` and `:`,
Other identifiers, such as `"calculate"`, `"FROM"`, as well as symbols such as `->` and `:` etc.,
are parsed in the order defined within the custom syntax.