monic part 5: writing C programs on the calculator

[Jonathan Busby]

(02-17-2021 09:14 AM)F-73P Wrote:  Thanks Jonathan for your helpful advice, always appreciated.

You're welcome

Quote:I removed "int" from the type_specifier grammar production and replaced it with "apq" (arbitrary precision rational), "apf" (arbitrary precision float - not supported on the calculator yet) and "int32_t" (maybe?).

I also added "read" and "write" from the TINY programming language, and post increment and decrement operators (just to increment/decrement variables for now, not used in assignments).

Nice Keep up the good work

Quote:There were a few aspects of the original BNF grammar I found confusing:

1) expression_stmt -> expression ; | ;

I couldn't figure out what the ; on its own is for, so I changed the production to

expression_stmt -> expression ;

This is to allow empty expressions. You need this in cases such as :

Code:

while(x != somevalue) ;

Which could be used for busy waiting ( eg. a "spinlock" )

Quote:2) expression -> var = expression | simple expression

At first I thought this was a typo as I couldn't see how you can have e.g.

expression -> var = expression
Replace non-terminal expression with var = expression to obtain:
expression -> var = var = expression

e.g. a=b=100

and so I changed the production to

expression -> var = simple expression | simple expression

But then I saw your comment explaining that = is right-associative and that a=b=100 is indeed legal. So I'll go back and fix that

Yep In the EBNF grammar it is :

Code:

expression =  { var , "=" } , simple-expression ;

Quote:I added some code generation instructions to the parser and now simple C programs like the factorial program below can be executed:

Nice work! I look forward to seeing how your project evolves

Regards,

Jonathan