70 lines
2.5 KiB
Go
70 lines
2.5 KiB
Go
// In this example, a parser is created that is able to parse input that looks
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// like "Hello, <name>!", and that extracts the name from it.
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//
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// The implementation uses only parser/combinator Handler functions and does
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// not implement a full-fledged state-based Parser for it. If you want to see the
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// same kind of functionality, implementated using a Parser, take a look at the
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// other hello examples.
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package examples
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import (
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"fmt"
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"git.makaay.nl/mauricem/go-parsekit/tokenize"
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)
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func Example_helloWorldUsingTokenizer() {
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tokenizer := createHelloTokenizer()
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for i, input := range []string{
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"Hello, world!",
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"HELLO ,Johnny!",
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"hello , Bob123!",
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"hello Pizza!",
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"Oh no!",
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"Hello, world",
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"Hello,!",
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} {
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output, err := tokenizer(input)
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if err != nil {
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fmt.Printf("[%d] Input: %q Error: %s\n", i, input, err)
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} else {
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fmt.Printf("[%d] Input: %q Output: %s\n", i, input, output)
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}
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}
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// Output:
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// [0] Input: "Hello, world!" Output: world
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// [1] Input: "HELLO ,Johnny!" Output: Johnny
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// [2] Input: "hello , Bob123!" Output: Bob123
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// [3] Input: "hello Pizza!" Output: Pizza
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// [4] Input: "Oh no!" Error: mismatch at start of file
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// [5] Input: "Hello, world" Error: mismatch at start of file
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// [6] Input: "Hello,!" Error: mismatch at start of file
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}
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// ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
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// Implementation of the parser
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// ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
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func createHelloTokenizer() tokenize.Func {
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// Easy access to parsekit definition.
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c, a, m := tokenize.C, tokenize.A, tokenize.M
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// Using the parser/combinator support of parsekit, we create a Handler function
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// that does all the work. The 'greeting' Handler matches the whole input and
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// drops all but the name from it.
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hello := a.StrNoCase("hello")
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comma := c.Seq(c.Optional(a.Blanks), a.Comma, c.Optional(a.Blanks))
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separator := c.Any(comma, a.Blanks)
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name := c.OneOrMore(c.Not(a.Excl))
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greeting := m.Drop(hello).
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Then(m.Drop(separator)).
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Then(name).
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Then(m.Drop(a.Excl)).
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Then(a.EndOfFile)
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// Create a Tokenizer that wraps the 'greeting' Handler and allows
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// us to match some input against that handler.
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return tokenize.New(greeting)
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}
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