mirror of
https://github.com/josdejong/mathjs.git
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50 lines
1.4 KiB
JavaScript
50 lines
1.4 KiB
JavaScript
var math = require('../../index')
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// Filter an expression tree
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console.log('Filter all symbol nodes "x" in the expression "x^2 + x/4 + 3*y"')
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var node = math.parse('x^2 + x/4 + 3*y')
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var filtered = node.filter(function (node) {
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return node.isSymbolNode && node.name === 'x'
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})
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// returns an array with two entries: two SymbolNodes 'x'
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filtered.forEach(function (node) {
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console.log(node.type, node.toString())
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})
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// outputs:
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// SymbolNode x
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// SymbolNode x
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// Traverse an expression tree
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console.log()
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console.log('Traverse the expression tree of expression "3 * x + 2"')
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var node1 = math.parse('3 * x + 2')
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node1.traverse(function (node, path, parent) {
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switch (node.type) {
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case 'OperatorNode': console.log(node.type, node.op); break
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case 'ConstantNode': console.log(node.type, node.value); break
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case 'SymbolNode': console.log(node.type, node.name); break
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default: console.log(node.type)
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}
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})
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// outputs:
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// OperatorNode +
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// OperatorNode *
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// ConstantNode 3
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// SymbolNode x
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// ConstantNode 2
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// transform an expression tree
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console.log()
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console.log('Replace all symbol nodes "x" in expression "x^2 + 5*x" with a constant 3')
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var node2 = math.parse('x^2 + 5*x')
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var transformed = node2.transform(function (node, path, parent) {
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if (node.isSymbolNode && node.name == 'x') {
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return new math.expression.node.ConstantNode(3)
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} else {
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return node
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}
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})
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console.log(transformed.toString())
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// outputs: '(3 ^ 2) + (5 * 3)'
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