a + b resembles line 34, which returns a parse tree (‘add’, (‘var’, ‘a’), (‘var’, ‘b’)). Therefore, according to the program above, a = 10 resembles line 22. Here all of them are made into token stream line-by-line and parsed line-by-line. Let’s say you want something like shown below. The parser should also parse in arithmetic operations, this can be done by expressions. Thus, we have build a basic lexer that converts the character stream to token stream. We do the same thing with new line character. Whenever we find “//”, we ignore whatever that comes next in that line.
#BASIC PROGRAMMING LANGUAGE COMPILER FREE#
We are doing a basic programmable script, so let’s just make it with integers, however, feel free to extend the same for decimals, long etc., We can also make comments. Whenever we find digit/s, we should allocate it to the token NUMBER and the number must be stored as an integer. This can be defined by the regular expression \”.*?\”. STRING tokens are string values and are bounded by quotation marks(” “). Then we also create the basic literals like ‘=’, ‘+’ etc., NAME tokens are basically names of variables, which can be defined by the regular expression *. In any programming language, there will be space between two characters. Thus we will need some basic tokens such as NAME, NUMBER, STRING. Let’s make a compiler that makes simple arithmetic operations. Now let’s build a class BasicLexer which extends the Lexer class from SLY. Difference between High Level and Low level languages.
#BASIC PROGRAMMING LANGUAGE COMPILER HOW TO#
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