Rz language

(This compiler is still a work in progress. For an older system (generate code for S2 processor), please visit the Rz compiler tools kit page )

Rz is aimed to be a teaching language for system programming and computer architecture subjects, which emphasises a small language that can be used to illustrate all the "inner" working parts of a computer system (compilation, code generation, ISA simulation), in other words it allows students to "play" with the system. In a way, Rz "looks like" C (without type).

Short description

The language is a small subset of C look-alike language. It has no type (or having only one type which is "int"). Global variables must be declared but local variables are automatic. A variable can be either a scalar or an array. There is no user defined data type. An array is one dimension. Rz language can be summarised as follows:

It has only integer as primitive data. (natural size depends on implementation)
Global variables must be declared before their use. Local variables are automatic (not required to be declared).
Global variables can be array. The size of array must be known at compile time. An array has only one dimension. Local variables can be only scalar.
Reserved words are: if, else, while, return, print.
Operators are: +, -, *, /, ==, !=, <, <=, >, >=, !, &&, ||, * (dereference), & (address).

For C programmer, please note, no: for, break, do, missing many operators especially ++, --
In version 3.5, it has a new syntax, using indentation instead of { } and newline instead of ;

Examples

It is easier just to look at an example to know most of the syntax. Here is an example of Rz

    // find max in an array
    a[10], N

    init()
      i = 0
      while ( i < N )
        a[i] = i
        i = i + 1

    main()
      N = 10
      init()
      max = a[0]
      i = 1
      while( i < N )
        if( max < a[i] ) max = a[i]
        i = i + 1
      print( "the max value is ", max )

The variables a[], N are globals, max, i are locals. For an array, the size must be known at compile time. (A note of C user, there is no ++, --, and no "break", "print" is not "printf"). "print" knows only integer and string. The size of basic unit (integer) depends on the target machine.

increment(x)
*x = *x + 1

main()
a = 1
increment(&a)
print(a)

The call by reference can be achieved using the * and & operators just like in C. In short, you can think of Rz syntax as C without type declaration.

History

Rz is a descendant of R1, a concurrent language for small control applications. (Have a look at full report and implementation from my research work web page). R1 is a concurrent language. Rz simplifies that by eliminating all the real-time concurrency language features and retains only the most basic language constructs.

Current state of implementation

Rz (version 3) is a work in progress. This is a new implementation of Rz language. The new parser generator is written. The grammar of Rz language is simplified. The compiler is modified to output a parse-tree. The parse-tree is an intermediate and explicit representation. A separate code generator can be written for any desired target processor. (The original Rz is compiled into its own byte-code. The original system also included a byte-code interpreter. For more information about the original system please visit old Rz-language )

rz3 included:

comp: the whole compiler
lexgen: lexical analyser generator

pgen-c: parser generator, the input is "rz-grammar9.txt"

rz3 version 1.0 include its "meta-interpreter". readme
rz3 version 2.0 is an excercise in code generation. It outputs a linear-code (assembly-like) to illustrate how to traverse and transform Rz parse-tree. See example of output.
rz3 version 3.3 outputs s-code (version som-v2). The output object code is run under Som-v2 virtual machine.
rz3 version 3.5 with pre-processing of input to use indentation as { } and \n as ";". The output is s-code (som-v2).

A session in Rz (version 3.5)

It has a new syntax, using indentation instead of { } and newline instead of ;
Here is an example of the new form:

fac(n)
if( n == 0 ) return 1
else return n * fac(n-1)

main()
print(fac(6))

Try to compile "fac.txt" shown here:

Here is the command line and the output at the screen:

D:\prabhas\bag\rz35\test>rz35 fac.txt
fac
main
(fun main (print (call fac 6 )))
(fun fac (else (== #1 0 )(return 1 )(return (* #1 (call fac (- #1 1 ))))))

:main
    fun.1
    lit.6
    call.fac
    sys.1
    ret.1
:fac
    fun.1
    get.1
    lit.0

. . .
You will get the file "fac.obj" as an output file. It is an object file that is executable under Som VM (a kind of virtual machine similar to JVM). You can "run" it under somv2x.

D:\prabhas\bag\rz\rz33\test>somv2x fac.obj
720

That's it. Enjoy!

Code Release

12 Nov 2010    rz3.zip
16 Nov 2010    rz31.zip    readme
28 Nov 2010    rz32.zip
28 Aug 2011     rz33.zip   rz33-1.zip (bug fix)
1 Sept 2011      rz35.zip   with a new look see example bubble.txt
26 Sept 2011    rz35-1.zip (bug fix and include "syscall") readme
13 July 2013    rz35-2.zip (refresh, no executable)

last update 13 July 2013