Subleq: Difference between revisions

{{out}}

<pre>

Hello, world!

</pre>

=={{header|XPL0}}==

{{trans|ALGOL W}}

<syntaxhighlight lang "XPL0">\Subleq program interpreter

\Executes the program specified in scode, stops when the instruction

\ pointer becomes negative.

procedure RunSubleq ( SCode, CodeLength);

integer SCode, CodeLength;

define MaxMemory = 3 * 1024;

integer Memory ( MaxMemory );

integer IP, A, B, C, I;

begin

begin

for I := 0 to MaxMemory - 1 do Memory( I ) := 0;

\Load the program into Memory

for I := 0 to CodeLength do Memory( I ) := SCode( I );

\Start at instruction 0

IP := 0;

\Execute the instructions to IP is < 0

while IP >= 0 do begin

\Get three words at IP and advance IP past them

A := Memory( IP );

B := Memory( IP + 1 );

C := Memory( IP + 2 );

IP := IP + 3;

\Execute according to A, B and C

if A = -1 then begin

\Input a character to B

Memory( B ) := ChIn(1)

end

else if B = -1 then begin

\Output character from A

ChOut(0, Memory ( A ) )

end

else begin

\Subtract and branch if <= 0

Memory( B ) := Memory( B ) - Memory( A );

if Memory( B ) <= 0 then IP := C

end

end \while-do

end

end \RunSubleq \;

\Test the interpreter with the hello-world program specified in the task

integer Code;

begin

Code := [ 15, 17, -1, 17, -1, -1

, 16, 1, -1, 16, 3, -1

, 15, 15, 0, 0, -1, 72

, 101, 108, 108, 111, 44, 32

, 119, 111, 114, 108, 100, 33

, 10, 0 ];

RunSubleq( Code, 31 )

end</syntaxhighlight>