`preserveLatex` doesn't preserve LaTeX in `3x+y`

[bengolds]

The preserveLaTeX option works most of the time, but it misses preserving the LaTeX at a level sometimes. For example, in the expression 3x+y, you get:

{
  latex: '3x+y',
  fn: [
    'Add',
    [ 'Multiply', { num: '3', latex: '3' }, { latex: 'x', sym: 'x' } ], // This is short form! We'd expect long form with latex.
    { latex: 'y', sym: 'y' }
  ]
}

// instead of

{
  latex: '3x+y',
  fn: [
    'Add',
    {
      latex: '3x'
      fn: [ 'Multiply', { num: '3', latex: '3' }, { latex: 'x', sym: 'x' } ]},
    }
    { latex: 'y', sym: 'y' }
  ]
}

Quick Repro:

node - << 'EOF'
    const util = require('util')
    const CE = require("@cortex-js/compute-engine")
    const myParse = new CE.LatexSyntax({preserveLatex: true})
    console.log(util.inspect(myParse.parse('3x+y'), {depth: null}))
EOF

This prints out:

[arnog]

@bengolds Do you expect latex to be present even for trivial cases, i.e. when a symbol or number and the latex is the same as the value of the expression?

That is:

x → { latex: "x", sym: "x"} or { sym: "x" }

2 → { latex: "2", num: "2"} or { num: "2" }

[bengolds]

For Symbol, StringLiteral, or Number, we don't expect it or store it. We're perfectly content ignoring it :)

For Function, we do need it so that we can turn fragments of the MathJson back into LaTeX. Without the LaTeX present, we'd basically have to rewrite ComputeEngine.serialize() 😅

[strickinato]

This appears to still be an issue in 0.4.3.

(Repro now with new API)

node - << 'EOF'                                                                                                                                         ~/work/compute-engine
    const util = require('util')
    const CE = require("@cortex-js/compute-engine")
    const myParse = new CE.ComputeEngine().latexSyntax // preserveLatex appears to be default now
    console.log(util.inspect(myParse.parse('3x+y'), {depth: null}))
EOF

[bengolds]

This is fixed in 0.6.0 if you use:

const ce = new ComputeEngine();
ce.jsonSerializationOptions.metadata = ['latex'];
ce.jsonSerializationOptions.shorthands = [];