Hello,please check Section 16.1.10 of Specifying Systems, which discusses strings and characters and even contains a function to convert lower-case letters to ASCII. In short, TLA+ has no hardwired definition of what characters are. In your representation, the variables in_pattern and in_text are sequences of strings, not characters.As far as I can tell, the algorithm is independent of any concrete representation of characters. I suggest that you make the set of characters as well as the inputs to the algorithm parameters of your specification, i.e. introduce (at the top of the module)CONSTANT Character, text, patternASSUME text \in Seq(Character) /\ pattern \in Seq(Character)When you use TLC to check your algorithm, you can instantiate these constants by concrete values, e.g.Character <- {a,b,c}  \* a set of model valuestext <- << a, a, b, a, c >>pattern <- << b, a >>In this way, you'll also alleviate the effect of state explosion. If you want to go further than testing the algorithm on concrete inputs, you can replace the parameters text' and pattern' by variables and nondeterministically assign them finite (bounded-length) sequences of characters by writing something likedefine {  \* sequences of characters of length at most n  CharSeq(n) == UNION { [1 .. k -> Character] : k \in 0 .. n }}[...]variables text \in CharSeq(5), pattern \in CharSeq(3);[...]In this way, TLC will check the algorithm for all text / pattern strings of bounded length.Remember that TLA+ is a language for specifying algorithms at a high level of abstraction, not a programming language. Hope this helps,StephanOn 15 Dec 2022, at 05:53, mohan radhakrishnan wrote:Hello,           I was looking for functions to get the ASCII value of characters but realized I couldn'tfind a list of all functions available. Should I look for a facility to add my own functions ?Can I check if the code returns the correct value before checking the model and state spaces ? The state space for this is enormous anyway.Thanks,Mohan -- You received this message because you are subscribed to the Google Groups "tlaplus" group. To unsubscribe from this group and stop receiving emails from it, send an email to tlaplus+unsubscribe@xxxxxxxxxxxxxxxx. To view this discussion on the web visit https://groups.google.com/d/msgid/tlaplus/6c72f651-82f0-416c-b01f-744a7bef5662n%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "tlaplus" group. To unsubscribe from this group and stop receiving emails from it, send an email to tlaplus+unsubscribe@xxxxxxxxxxxxxxxx. To view this discussion on the web visit https://groups.google.com/d/msgid/tlaplus/ECAA9F9A-1BE6-4CB9-A832-56E384F2A9D8%40gmail.com.