51 lines
1.2 KiB
JavaScript
51 lines
1.2 KiB
JavaScript
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/**
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* Function transforms
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*
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* When using functions via the expression parser, it is possible to preprocess
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* function arguments and post process a functions return value by writing a
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* *transform* for the function. A transform is a function wrapping around a
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* function to be transformed or completely replaces a function.
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*/
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const { create, all } = require('../..')
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const math = create(all)
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// create a function
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function addIt (a, b) {
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return a + b
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}
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// attach a transform function to the function addIt
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addIt.transform = function (a, b) {
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console.log('input: a=' + a + ', b=' + b)
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// we can manipulate the input arguments here before executing addIt
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const res = addIt(a, b)
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console.log('result: ' + res)
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// we can manipulate the result here before returning
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return res
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}
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// import the function into math.js
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math.import({
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addIt: addIt
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})
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// use the function via the expression parser
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console.log('Using expression parser:')
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console.log('2+4=' + math.evaluate('addIt(2, 4)'))
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// This will output:
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//
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// input: a=2, b=4
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// result: 6
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// 2+4=6
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// when used via plain JavaScript, the transform is not invoked
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console.log('')
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console.log('Using plain JavaScript:')
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console.log('2+4=' + math.addIt(2, 4))
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// This will output:
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//
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// 6
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