less_retarded_wiki/bytecode.md
2023-10-28 14:40:53 +02:00

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# Bytecode
TODO
## Example
Let's consider a simple algorithm that tests the [Collatz conjecture](collatz_conjecture.md) (which says that applying a simple operation from any starting number over and over will always lead to number 1). The algorithm in [C](c.md) would look as follows:
```
// Collatz conjecture
#include <stdio.h>
int next(int n)
{
return n % 2 ? // is odd?
3 * n + 1 :
n / 2;
}
int main(void)
{
int n = getchar() - '0'; // read input ASCII digit
while (1)
{
printf("%d\n",n);
if (n == 1)
break;
n = next(n);
}
return 0;
}
```
The program reads a number (one digit for simplicity) and then prints the sequence until reaching the final number 1. Now let's rewrite the same algorithm in [comun](comun.md), a language which will allow us to produce bytecode:
```
# Collatz conjecture
next:
$0 2 % ? # is odd?
3 * 1 +
;
2 /
.
.
<- # read input ASCII digit
"0" - # convert it to number
@@
# print:
$0 10 / "0" + ->
$0 10 % "0" + ->
10 ->
$0 1 = ?
!@
.
next
.
```
Here is annotated bytecode this compiles to:
```
000000: DES 00 0111 # func \ next:
000001: JMA 00 0100... # 20 (#14) |
000002: COC 00 0001 |
000003: MGE 00 0000 | $0
000004: CON' 00 0010 # 2 (#2) | 2
000005: MOX 00 0000 | %
000006: DES 00 0001 # if | \ ?
000007: JNA 00 0000... # 16 (#10) | |
000008: COC 00 0001 | |
000009: CON' 00 0011 # 3 (#3) | | 3
00000a: MUX 00 0000 | | *
00000b: CON' 00 0001 # 1 (#1) | | 1
00000c: ADX 00 0000 | | +
00000d: DES 00 0010 # else | < ;
00000e: JMA 00 0011... # 19 (#13) | |
00000f: COC 00 0001 | |
000010: CON' 00 0010 # 2 (#2) | | 2
000011: DIX 00 0000 | | /
000012: DES 00 0011 # end if | / .
000013: RET 00 0000 / .
000014: INI 00 0000
000015: INP 00 0000 <-
000016: CON' 00 0000... # 48 (#30) "0"
000017: COC 00 0011
000018: SUX 00 0000 -
000019: DES 00 0100 # loop \ @@
00001a: MGE 00 0000 | $0
00001b: CON' 00 1010 # 10 (#a) | 10
00001c: DIX 00 0000 | /
00001d: CON' 00 0000... # 48 (#30) | "0"
00001e: COC 00 0011 |
00001f: ADX 00 0000 | +
000020: OUT 00 0000 | ->
000021: MGE 00 0000 | $0
000022: CON' 00 1010 # 10 (#a) | 10
000023: MOX 00 0000 | %
000024: CON' 00 0000... # 48 (#30) | "0"
000025: COC 00 0011 |
000026: ADX 00 0000 | +
000027: OUT 00 0000 | ->
000028: CON' 00 1010 # 10 (#a) | 10
000029: OUT 00 0000 | ->
00002a: MGE 00 0000 | $0
00002b: CON' 00 0001 # 1 (#1) | 1
00002c: EQX 00 0000 | =
00002d: DES 00 0001 # if | \ ?
00002e: JNA 00 0100... # 52 (#34) | |
00002f: COC 00 0011 | |
000030: DES 00 0101 # break | | !@
000031: JMA 00 1000... # 56 (#38) | |
000032: COC 00 0011 | |
000033: DES 00 0011 # end if | / .
000034: CAL 00 0011 # 3 (#3) | next
000035: DES 00 0110 # end loop / .
000036: JMA 00 1010... # 26 (#1a)
000037: COC 00 0001
000038: END 00 0000
```
TODO: analyze the above, show other bytecodes (python, java, ...)