Question

Given that myVector is a vector and i is an index , when I do this :

(= (vector-ref myVector i) #\.) 

I get :

=: contract violation
  expected: number?
  given: #\.
  argument position: 1st
  other arguments...:
   #\.

How can I check if the character at location i is a . ?

Answer 1

You should not convert the character to a number, simply use the char=? procedure, from the documentation:

Returns #t if all of the arguments are eqv?

For your example in particular:

(define myVector #(#\1 #\. #\2))
(define i 1)

(char=? (vector-ref myVector i) #\.)
=> #t

Several of your questions of the last couple of days have been related to character or string manipulation, I’d advise you take a good look at the documentation page dealing with those subjects.