How Can I Simulate Negative Lookbehind Assertions in Go Regular Expressions?

Simulating Negative Lookbehind in Go

Your original regex, featuring a negative lookbehind assertion, aims to extract commands without any preceding @, #, or / characters. However, Go does not support negative lookbehinds, posing a hurdle in implementing this pattern.

Rewriting the Regex

To achieve the same functionality without negative lookbehinds, we can replace the characters to be excluded within the character set:

[^@#/]\w.*

If commands are not allowed to begin with these characters, we can use the ^ anchor to enforce this condition:

(?:^|[^@#\/])\b\w.*

Alternative Approach Using Go Functions

Alternatively, consider using Go functions to filter and process the input string:

func Filter(vs []string, f func(string) bool) []string { ... }

func Process(inp string) string {
    t := strings.Split(inp, " ")
    t = Filter(t, func(x string) bool {
        return strings.Index(x, "#") != 0 &&
            strings.Index(x, "@") != 0 &&
            strings.Index(x, "/") != 0
    })
    return strings.Join(t, " ")
}

This approach leverages a filter function to exclude words beginning with the specified characters, then stitches the remaining words back into a new string. You can find a working demonstration on the Go playground at http://play.golang.org/p/ntJRNxJTxo.

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