Function subStringEval

expr/builtins/string.go:186–217

(ctx expr.EvalContext, vals []value.Value)

	return subStringEval, nil
}
func subStringEval(ctx expr.EvalContext, vals []value.Value) (value.Value, bool) {

	if vals[0] == nil || vals[0].Err() || vals[0].Nil() {
		return nil, false
	}
	if vals[1] == nil || vals[1].Err() || vals[1].Nil() {
		return nil, false
	}

	inputStr := vals[0].ToString()

	idx, ok := value.ValueToInt(vals[1])
	if !ok || idx < 0 {
		return nil, false
	}
	if len(inputStr) < idx {
		return nil, false
	}

	if len(vals) == 3 {
		idx2, ok := value.ValueToInt(vals[2])
		if !ok || idx2 < 0 {
			return nil, false
		}
		if len(inputStr) < idx2 {
			return nil, false
		}
		return value.NewStringValue(inputStr[idx:idx2]), true
	}

	return value.NewStringValue(inputStr[idx:]), true
}

// Strip a string, removing leading/trailing whitespace
//