Github user dkuppitz commented on the issue:
https://github.com/apache/tinkerpop/pull/729
You can add a static compiled regex pattern:
```
private static final Pattern EQUATION_PATTERN =
Pattern.compile("\\b(?!abs|acos|asin|atan|cbrt|ceil|cos|cosh|exp|floor|log|log10|log2|sin|sinh|sqrt|tan|tanh|signum)(_|([A-Za-z][A-Za-z0-9]*))\\b");
```
...then `getVariables()` can be as simple as:
```
protected static final Set<String> getVariables(final String equation) {
final Matcher matcher = EQUATION_PATTERN.matcher(equation);
final Set<String> variables = new LinkedHashSet<>();
while (matcher.find()) {
variables.add(matcher.group());
}
return variables;
}
```
And perhaps to increase the readability and maintainability, we should do
something like this:
```
private static final String[] FUNCTIONS = new String[] {
"abs", "acos", "asin", "atan",
"cbrt", "ceil", "cos", "cosh",
"exp",
"floor",
"log", "log10", "log2",
"signum", "sin", "sinh", "sqrt",
"tan", "tanh"
};
private static final Pattern EQUATION_PATTERN = Pattern.compile("\\b(?!" +
String.join("|", FUNCTIONS) + ")(_|([A-Za-z][A-Za-z0-9]*))\\b");
```
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