Arithmetic Functions work even when not loaded

[maorfaingold]

I'm using custom evaluate with only evaluateDependencies but still some of the arithmetic functions are working:

const { create, evaluateDependencies } = require('mathjs')

const { evaluate } = create({
  evaluateDependencies
})

console.log(evaluate('2 - 1')) // correctly fails because subtract is not defined
console.log(evaluate('3 / 3')) // correctly fails because divide is not defined

console.log(evaluate('2 + 3')) // succeeds even though add is not defined
console.log(evaluate('2 * 3')) // succeeds even though multiply is not defined
console.log(evaluate('2 ^ 3')) // succeeds even though pow is not defined

(there may be more arithmetic functions that are working I didn't checked them all)

there is a similar issue: #2876
but there the issue was with 'det' and the suggested solution was to use
require('mathjs/number')

I'm not sure this solution will solve my issue but can't know for sure because mathjs/number missing typescript definitions as described in this open issue:
#2506

[josdejong]

Thanks for your input.

Missing TypeScript definitions for 'mathjs/number' is discussed in #2506

Can you explain what you try to achieve? If you want to disable specific operators, you could do something like the following:

• Parse the expression via math.parse
• Using .filter(), check if the parsed expression contains OperatorNodes that have a .op property that you want to disable.
• If those are found, throw an error like "Operator +" not supported.

See docs about parse and filter: https://mathjs.org/docs/expressions/expression_trees.html

[maorfaingold]

@josdejong
In my specific case I want a textbox that allows only numbers, if the user's input contains any arithmetic operators I want it to throw an error.

In my case I use:

const { create, evaluateDependencies, unaryMinusDependencies } = require('mathjs')

const { evaluate } = create({
  evaluateDependencies,
  unaryMinusDependencies  // to allow negative numbers (not a must - also part of the described issue)
})

to create a custom evaluate that should throw an error if the user's input includes any operators.

Sure there are workarounds for the issue, mine looks like this:

const { create, factory, evaluateDependencies, unaryMinusDependencies } = require('mathjs')

const { evaluate } = create({
  evaluateDependencies,
  unaryMinusDependencies,  // to allow negative numbers (not a must - also part of the described issue)
  createAdd: factory('add', [], () => () => { throw new Error('Error: Function add missing in provided namespace "math"'); } ),
  createMultiply: factory('multiply', [], () => () => { throw new Error('Error: Function multiply missing in provided namespace "math"'); } ),
 createPow: factory('pow', [], () => () => { throw new Error('Error: Function pow missing in provided namespace "math"'); } )
})

this way I can mimic the expected behavior (the same as with substract and divide).

The issue is not critical and have pretty simple workarounds but it's an issue in the code - the expected behavior is if I create a custom evaluate using only 'evaluateDependencies' all the arithmetic operators should not be imported (surely not partially imported - in this case 'subtract' and 'divide' throw errors and the rest not - 'add', 'multiply', 'pow', and also unaryMinus works when not using 'unaryMinusDependencies'.

[josdejong]

In my specific case I want a textbox that allows only numbers

That sounds like you do not need mathjs at all? If the input is just a number you can use JavaScript's parseFloat or parseInt.

[maorfaingold]

I oversimplified my use case - I need to support any possible combination of arithmetic functions. One of the cases is not supporting any functions at all as I described above, other cases the user may want only add and subtract, or maybe only multiple and divide, or all functions except log etc.

[josdejong]

In that case I think the best way is to parse the expression into an expression tree and validate this according to the limitations you want to apply, like I explained in #3200 (comment).