After getting so curious about how a interpreter works internally I decieded to develop my own interpreted language. And the result is oboni. I am still working on removing its bugs and add new features.
My current approch is so simple. Lexer -> Parser -> Interpret
For lexer and parser I didnt used any third party. All hand coded. As my intend is to learn in depth. The interpreter for Oboni is developed in C.
#Lexer
lexer.h and lexer.c, those are the files that working for lexical analysis. Also for regular expression I coded some finite state machines that can be found in fsm.h and fsm.c files.
#Parser
An Abstract Syntax Tree is getting build after getting token list from lexer. I tried to keep it simple. Grammers that are used for parser are-
EXPRESSION -> STATEMENT EXPRESSION_PRIME | CONTROLFLOW EXPRESSION_PRIME | EPSILON
EXPRESSION' -> STATEMENT '\n' EXPRESSION | CONTROLFLOW '\n' EXPRESSION | EPSILON
STATEMENT -> var identifier | = identifier TERM | show TERM
CONTROLFLOW -> if '(' EVALUATION ')' BLOCK | when '(' EVALUATION ')' BLOCK
BLOCK -> '{' EXPRESSION_PRIME '}' EXPRESSION_PRIME
TERM -> identifier | number | string | '(' EVALUATION ')'
EVALUATION -> operator TERM TERM
As you guessed I tried to implement Polish prefix notation for equations or statements. Because it gave me somewhat relif for operator precedence checking.
So a simple Oboni program looks like this -
var x
= x 1
when(< x 100){
show x
= x (+ x 1)
}That show is currently just working like a keyword but I will move to functions when I will implement functions in my language.