Update

2023-10-21 00:02:20 +02:00 · 2023-10-21 00:02:20 +02:00 · 671c98ff3a
commit 671c98ff3a
parent 99e8181bdc
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--- a/bytecode.md
+++ b/bytecode.md
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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
+.
+```
+
+The bytecode this compiles to is following:
+
+```
+000000: DES  00 0111    # func
+000001: JMA  00 0100... # 20 (#14)
+000002: COC  00 0001
+000003: MGE  00 0000
+000004: CON' 00 0010    # 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)
+00000a: MUX  00 0000
+00000b: CON' 00 0001    # 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)
+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)
+000017: COC  00 0011
+000018: SUX  00 0000
+000019: DES  00 0100    # loop
+00001a: MGE  00 0000
+00001b: CON' 00 1010    # 10 (#a)
+00001c: DIX  00 0000
+00001d: CON' 00 0000... # 48 (#30)
+00001e: COC  00 0011
+00001f: ADX  00 0000
+000020: OUT  00 0000
+000021: MGE  00 0000
+000022: CON' 00 1010    # 10 (#a)
+000023: MOX  00 0000
+000024: CON' 00 0000... # 48 (#30)
+000025: COC  00 0011
+000026: ADX  00 0000
+000027: OUT  00 0000
+000028: CON' 00 1010    # 10 (#a)
+000029: OUT  00 0000
+00002a: MGE  00 0000
+00002b: CON' 00 0001    # 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)
+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, ...)