Cryptol_04_flow equation/synonym/class/module

Cryptol stream equation/synonym/class/module

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Flow equation

1. For the shift feedback register in the figure below, the description code is as follows:
   

   as = [0x3F, 0xE2, 0x65, 0xCA] # new
   where
   new = [ a ^ b ^ c | a <- as
   | b <- drop`{
         
         1} as
   | c <- drop`{
         
         3} as ]
   

Synonym

1. Similar to the definition of typedef in C language, but more powerful and can be parameterized;

   type Word8 = [8]
   type CheckedWord = (Word8, Bit)
   type Point a  = {
         
         x : [a], y : [a]}
   

Class//Class in Cpp is not a concept

1. Used to describe the behavior shared by multiple types, such as == to compare any single type and return a Boolean value;

   Cryptol> :t (==)
   (==) : {
         
         a} (Eq a) => a -> a -> Bit
   

Program structure with module

1. Similar to the concept of Verilog's module, a file can only have one module, and the module and the file name are the same;

2. The first line of non-commented code in the file should be:

   module utilities where

3. If you want to use other modules, you can use the following definitions, and the corresponding files will be searched in the current directory:

   import utilities

4. Private variables, similar to Cpp, prevent the data of your own module from being accessed;

   private internalDouble x = x + x
   exportedDouble = x * 2
   

It's hard to understand by just looking at the description document, the next step is to look at it in conjunction with the code!