https://github.com/luochen1990/ast-reducer
A Tool to process AST or any other recursive data structure in JavaScript.
https://github.com/luochen1990/ast-reducer
Last synced: over 1 year ago
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A Tool to process AST or any other recursive data structure in JavaScript.
- Host: GitHub
- URL: https://github.com/luochen1990/ast-reducer
- Owner: luochen1990
- License: mit
- Created: 2018-01-16T07:11:29.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2018-11-06T09:29:32.000Z (over 7 years ago)
- Last Synced: 2025-02-21T07:06:05.551Z (over 1 year ago)
- Language: CoffeeScript
- Size: 9.77 KB
- Stars: 1
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
AST Reducer
===========
A Tool to process AST or any other recursive data structure in JavaScript.
Features
--------
- An EDSL to define reduce rules
- Pure functional:
- state is managed via simulating a state monad (the `state` field in context)
- global constants is managed via simulating a reader monad (the `env` field in context)
- Derivable Reducer
- Pretty and helpful error message
- Configuable node parsing logic (the `parseNode` field in opts)
- Configuable default rule (the `defaultRule` field in opts)
Install
-------
```
npm install ast-reducer
```
Usage
-----
In CoffeeScript
#### Simple Usage
```coffeescript
{defineReducer} = require('ast-reducer')
evalExpr = defineReducer({name: 'ArithCalc'}) (def) ->
def('+') ([a, b]) -> @(a) + @(b)
def('-') ([a, b]) -> @(a) - @(b)
def('const') ([a]) -> parseFloat(a)
ast = ['+', ['-', ['const', 1], ['const', 2]], ['+', ['const', '4'], ['const', '8']]]
console.log evalExpr.eval(ast)
# output: 11
```
#### Use State
```coffeescript
evalExpr = defineReducer({name: 'ArithCalc0'}) (def) ->
def('+') ([a, b], {env, state}) -> state.cnt += 1; @(a) + @(b)
def('-') ([a, b], {env, state}) -> state.cnt += 1; @(a) - @(b)
def('const') ([a]) -> parseFloat(a)
context = {env: {}, initState: (-> {cnt: 0})}
console.log evalExpr.runState(ast, context)
# output: { result: 11, state: { cnt: 3 } }
```
#### Derive Reducer
```coffeescript
evalExpr2 = evalExpr.derive({name: 'ArithCalc1'}) (def) ->
def('*') ([a, b], {env, state}) -> state.cnt += 1; @(a) * @(b)
ast2 = ['+', ['-', ['const', 1], ['const', 2]], ['*', ['const', '4'], ['const', '8']]]
console.log evalExpr2.runState(ast2, context)
# output: { result: 31, state: { cnt: 3 } }
```
#### Error Report
```coffeescript
console.log evalExpr.runState(ast2, context)
### error message:
ReduceError:
[reducer]: "ArithCalc0"
[path]: ["+","*"]
[state]: {"cnt":2}
[current]: ["*",["const","4"],["const","8"]]
[input]: ["+",["-",["const",1],["const",2]],["*",["const","4"],["const","8"]]]
Caused By: UnimplementedRule: *
at Function.defaultRule (the/long/long/path/to/reducer.coffee:34:13)
at reduce (the/long/long/path/to/reducer.coffee:42:11)
at Object.runState (the/long/long/path/to/reducer.coffee:47:31)
...
###
```