Arithmetic evaluation: Difference between revisions
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(→ast standard library module: Lets modify the AST) |
(add mildly cheeky E example) |
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calcVis((new AST).parse(expression)) ; |
calcVis((new AST).parse(expression)) ; |
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}</lang> |
}</lang> |
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=={{header|E}}== |
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While the task requirements specify not evaluating using the language's built-in eval, they don't say that you have to write your own ''parser''... |
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<lang e>def eParser := <elang:syntax.makeEParser> |
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def LiteralExpr := <elang:evm.makeLiteralExpr>.asType() |
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def arithEvaluate(expr :String) { |
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def ast := eParser(expr) |
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def evalAST(ast) { |
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return switch (ast) { |
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match e`@a + @b` { evalAST(a) + evalAST(b) } |
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match e`@a - @b` { evalAST(a) - evalAST(b) } |
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match e`@a * @b` { evalAST(a) * evalAST(b) } |
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match e`@a / @b` { evalAST(a) / evalAST(b) } |
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match e`-@a` { -(evalAST(a)) } |
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match l :LiteralExpr { l.getValue() } |
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} |
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} |
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return evalAST(ast) |
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}</lang> |
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Parentheses are handled by the parser. |
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<lang e>? arithEvaluate("1 + 2") |
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# value: 3 |
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? arithEvaluate("(1 + 2) * 10 / 100") |
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# value: 0.3 |
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? arithEvaluate("(1 + 2 / 2) * (5 + 5)") |
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# value: 20.0</lang> |
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=={{header|Haskell}}== |
=={{header|Haskell}}== |
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