::: danger Exponentiation is ECMAScript 2016 New Features in ECMAScript 2016: JavaScript Exponentiation (**) See for instance: https://www.w3schools.com/js/js_2016.asp and https://262.ecma-international.org/7.0/
... This specification also includes support for a new exponentiation operator and adds a new method to Array.prototype called includes
Since escodegen does not support this Feature the combination of unary minus and exponentiation currently does not work.
➜ arith2js-parallel-computing-group-parallel git:(essay-2023-02-15-miercoles) ✗ node
Welcome to Node.js v18.8.0.
Type ".help" for more information.
> let espree = require('espree')
> let ast = espree.parse('(-2)**2') // gives an error since the default compiler is ecma 5
Uncaught [SyntaxError: Unexpected token *
> let ast3 = espree.parse('(-2)**2', { ecmaVersion: 7}) // no errors. Right AST
> let escodegen = require('escodegen')
> escodegen.generate(ast3) // escodegen does not support this feature
'-2 ** 2;' // the code generated is wrong
> let gc = escodegen.generate(ast3)
> gc
'-2 ** 2;'
> eval(gc) // the evaluation of the code produces errors
Uncaught:
SyntaxError: Unary operator used immediately before exponentiation expression. Parenthesis must be used to disambiguate operator precedence
> -2 ** 2 # JS does not accept this expression
-2 ** 2
^^^^^
Uncaught:
SyntaxError: Unary operator used immediately before exponentiation expression. Parenthesis must be used to disambiguate operator precedence
> (-2) ** 2 # ... But this code works
4
:::
Therefore, the following continuation of the former node session suggest the correct translation:
::: tip Use Math.pow
```js
> let ast5 = espree.parse('Math.pow(-2,2)')
undefined
> gc = escodegen.generate(ast5)
'Math.pow(-2, 2);'
> eval(gc)
4
:::