Undoc'd Feature?

[toml_12953]

Auto decrementing a variable appears to work in HPPL while incrementing doesn't.

Here's a snippet from a C program and an equivalent snippet in HPPL
Notice the assignment statement right in the IF statement.:

Code:


if (!(t=a[x]-a[--y]) || x-y==abs(t)){
  y=0;
  while(!--a[x])
    --x;
}

Code:


IF (NOT(T:=A(X)-A(--Y)) OR X-Y==ABS(T)) THEN
  Y:=0;
  WHILE NOT --A(X) DO
    --X;
  END;
END;