Finding string indices

I found a simple task that is surprisingly chellenging for the openai model. I pass a text in my prompt and instruct to display starting and ending indices of a substring/phrase from this text. The completion usually includes very wrong and often variable indices. I need it for a more complex task whose final result is to highlight parts of the text. That is why I need these indexes. I tried giving examples but nothing seems to work.

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As ChatGPT is a language model, sometimes it requires a bit of prompt engineering to get satisfactory results. ChatGPT predicts text and is not a calculator or program language interpreter.

Having said that, you can specifically prompt ChatGPT to write a method, for example, in your favorite programming language, and the models can write some nice code from time to time.

See, for example:

You can see that ChatGPT makes an error and labels one Ruby code block as Python, I assume this is because Python also has a puts method? Anyway, it’s not important as the code works.

So, basically, you can see how I do these things with OpenAI:


Write a Ruby method which accepts two strings as arguments, string 1 and string 2, and outputs the starting and ending indices of string 1 based on substring string 2.


Here’s a simple method that accepts two strings as arguments, and outputs the starting and ending indices of the first occurrence of string 2 in string 1:

def find_substring_indices(string1, string2) start_index = string1.index(string2) returnnil if start_index.nil? end_index = start_index + string2.length - 1 [start_index, end_index] end

For example:

puts find_substring_indices("hello world", "world") # Output: [6, 11]

Always confirm ChatGPT as a human :slight_smile:

MacStudio$ rails c
Loading development environment (Rails
irb(main):001:1* def find_substring_indices(string1, string2)
irb(main):002:1*   start_index = string1.index(string2)
irb(main):003:1*   return nil if start_index.nil?
irb(main):004:1*   end_index = start_index + string2.length - 1
irb(main):005:1*   [start_index, end_index]
irb(main):006:0> end
=> :find_substring_indices
irb(main):007:0> puts find_substring_indices("hello world", "world")
=> nil

Hope this helps.

@ruby_coder Thank you for your suggestion. The problem with this kind of solution is that it is not reliable enough. Even if fed with a proper function the model is inconsistent with its answers. So, I did it in a different way, although not that elegant. Because I needed the text from the prompt to be divided into sections, I require the first and the last sentence of each section. Based on that I can programmatically get my indices used later for text highlighting.