A compiler converts a source language program into a target language program. There are some basic stages in compilation process, including scanning, parsing, semantic analysis, and code generation. For this assignment, you will implement a scanner and parser for a small language with its grammar given in BNF notation. The language literals are enclosed with ' ' in the CFG below. Your task is to implement a scanner and a parser for this simple language. Let's name our language Blazer with .bl as program file extension. Context Free Grammar:
< program > -> < stmt > { < stmt >}'halt'
< stmt > -> ID '=' < expr >
|'read' ID
|'write' < expr >
< expr > -> < term > {('+'|'-') < term > }
< term > -> < factor > {('*'|'/') < factor > }
< factor > -> ID
| INT_CONSTANT
|'(' < expr > ')'

The possible set of tokens, represented with regular expressions, includes:
ASSIGN -> =
PLUS -> +
MINUS -> -
TIMES -> *
DIV -> /
LPAREN -> (
RPAREN -> )
ID -> letter(letter|digit)*
Except read, write, and halt.
INT_CONSTANT -> digit digit*
LETTER ->[a-zA-Z]
DIGIT ->[0-9]

Notes:

1. * means repeat zero or more times.
2. You may find strcmp useful for implementing reserved words/keywords in a language;
3. Programs can be read from file or keyboard, but files are recommended.