a-compiler

'A' language compiler, linker, stack machine assembler and executor - an educational project. The 'A' language is a mix of pascal/modula .. where the 'A' stands for Awfull. Here's an example :

program primes;
var     i,j;
var     flag;
var     dot;

begin
    i := 5;
    while ( i < 1000) do begin
            j := 2;
            while ( j <= (i - 1)) do begin
                    if ( i <> ((i/j) * j)) then
                     begin
                            j := j + 1;
                            flag := 0;
                     end;
                    else
                     begin
                            /* i is not prime
                            j := i;
                            flag := 1;
                     end;
            end;
            if (flag = 1 ) then
                    flag := 0;
            else
                    begin
                            flag := 0;
                            write(i);
                    end;
            i := i + 1;
    end;
end.

but the original complete syntax is lost ... :-)

The project is made of :

• ac - the compiler, based on bison and flex
• al - the linker
• aa - the stack machine assembler
• ax - the stack machine executer

Also the stack machine opcodes are lost :-) but you can see io.s library code for writestr function here :

        .module rts

io_char .word   1         // Buffer for output,input instructions
io_cnt  .word   1         // Counter for general pourpose
io_flag .word   1         // Sign flag

        .export writestr
        .export readstr
        .export write
        .export read

writestr:
        pushi   0          // Local counter for writestr
wrs_loop:
        pushr   1
        pushr   4          // Take length of string
        cmp
        jge     end_wrs    // If cnt > length string finish
        pushr   1          // Take cnt
        pushr   5          // Take address of string passed
        add
        push*              // Take value of cnt element of string passed
        pushr   1          // Dup last top of SP
        pop     io_char    // Put in global var io_char for output
        output  io_char
        pushi   10         // Line feed
        cmp
        jeq     end_wrs    // If LF end printing
        pushi   1
        add                // Add 1 to cnt
        jmp     wrs_loop   // Repeat with next element of string
end_wrs:
        spfree  1
        ret

...

or you can generate stack machine code with ac -S ... Code was written by me and a friend of mine (Franz) many years ago ... also the original friendship is lost.

Currently ac and aa do not work : I'm fixing them ...