simple-squiggle

A restricted subset of Squiggle
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convert_fraction_to_bignumber.js (2256B)

      1 // Convert from Fraction to BigNumber
      2 //
      3 // In the configuration of math.js one can specify the default number type to
      4 // be `number`, `BigNumber`, or `Fraction`. Not all functions support `Fraction`
      5 // or `BigNumber`, and if not supported these input types will be converted to
      6 // numbers.
      7 //
      8 // When `Fraction` is configured, one may want to fallback to `BigNumber`
      9 // instead of `number`. Also, one may want to be able to mix `Fraction` and
     10 // `BigNumber` in operations like summing them up. This can be achieved by
     11 // adding an extra conversion to the list of conversions as demonstrated in
     12 // this example.
     13 
     14 // Create an empty math.js instance, with only typed
     15 // (every instance contains `import` and `config` also out of the box)
     16 const { create, typedDependencies, all } = require('../..')
     17 const math = create({
     18   typedDependencies
     19 })
     20 
     21 // TODO: this should be much easier
     22 const allExceptLoaded = Object.keys(all)
     23   .map(key => all[key])
     24   .filter(factory => math[factory.fn] === undefined)
     25 
     26 // Configure to use fractions by default
     27 math.config({ number: 'Fraction' })
     28 
     29 // Add a conversion from Faction -> BigNumber
     30 // this conversion:
     31 // - must be inserted in the conversions list before the conversion Fraction -> number
     32 // - must be added to the conversions before loading functions into math.js
     33 math.typed.conversions.unshift({
     34   from: 'Fraction',
     35   to: 'BigNumber',
     36   convert: function (fraction) {
     37     return new math.BigNumber(fraction.n).div(fraction.d)
     38   }
     39 })
     40 
     41 // Import all data types, functions, constants, the expression parser, etc.
     42 math.import(allExceptLoaded)
     43 
     44 // Operators `add` and `divide` do have support for Fractions, so the result
     45 // will simply be a Fraction (default behavior of math.js).
     46 const ans1 = math.evaluate('1/3 + 1/4')
     47 console.log(math.typeOf(ans1), math.format(ans1))
     48 // outputs "Fraction 7/12"
     49 
     50 // Function sqrt doesn't have Fraction support, will now fall back to BigNumber
     51 // instead of number.
     52 const ans2 = math.evaluate('sqrt(4)')
     53 console.log(math.typeOf(ans2), math.format(ans2))
     54 // outputs "BigNumber 2"
     55 
     56 // We can now do operations with mixed Fractions and BigNumbers
     57 const ans3 = math.add(math.fraction(2, 5), math.bignumber(3))
     58 console.log(math.typeOf(ans3), math.format(ans3))
     59 // outputs "BigNumber 3.4"