can someone help me solve the following F# questions with ecplanations

1.A

In the Notes on Programming Language Syntax page, an example parser for a simple language is given, using C syntax. Write the parser using F#, but you may only use functional programming and immutable date.

Create the list of tokens as a discriminated union, which (in the simplest case) looks like an enumeration.

type TERMINAL = IF|THEN|ELSE|BEGIN|END|PRINT|SEMICOLON|ID|EOF

With this type declared, you can use the terminals like you would use enumerated values in Java.

Use immutable data. The C-code example uses mutable data. Pass the program into the start symbol function. Pass the input yet to be processed to each non-terminal function.

The main function might look like this:

let test_program program =

let result = program |> S

match result with

| [] -> failwith "Early termination or missing EOF"

| x::xs -> if x = EOF then accept() else error()

You do not have to parse input strings. Assume that the parsing has been done. Pass a list of tokens that represent a program into the start symbol. Try these program examples:

[IF;ID;THEN;BEGIN;PRINT;ID;SEMICOLON;PRINT;ID;END;ELSE;PRINT;ID;EOF]

[IF;ID;THEN;IF;ID;THEN;PRINT;ID;ELSE;PRINT;ID;ELSE;BEGIN;PRINT;ID;END;EOF]

Causes error:

[IF;ID;THEN;BEGIN;PRINT;ID;SEMICOLON;PRINT;ID;SEMICOLON;END;ELSE;PRINT;ID;EOF]

Print an accept message when the input is valid and completely consumed. Generate appropriate error messages for incorrect symbols, not enough input, and too much input.

B. Once you have the parser recognizing input, generate a parse tree using a discriminated type.