On Friday, 23 December 2022 at 00:58:01 UTC, Steven Schveighoffer
wrote:
Without the rest of the code, and how random is called, I have
a hunch... Are you using threads by any chance?
If, for instance, your calls to rand01 are done in a new
thread, that new thread will have a *default* state of Mt19937.
-Steve
Good question, Steve, but I do not intentionally start any
threads. Below is the machinery that interprets a for-loop. Do
you see anything that would enclose a previous state of the RNG?
```d
specialForms["for"] = function ExprInContext( ExprInContext eINc
){
// Execute a `for` loop, Default is to increment up by one
// 1. Parse loop args
Atom*[] loopArgs = flatten_atom_list( second( eINc.expr ) );
// Fetch args
string iVarName = loopArgs[0].str; //Get the counter var
name
bool incrByOne = (loopArgs.length == 3);
double loBound = 0.0;
double hiBound = 0.0;
double incr = 1.0;
double i /*---*/ = 0.0;
Atom* loopProg = third( eINc.expr ); // WARNING: TYPE NOT
CHECKED
Atom* rtnExpr = null;
Env* nuEnv = null;
ExprInContext runBlock;
// Case: Default loop increments by 1.0
if( incrByOne ){
loBound = loopArgs[1].num;
hiBound = loopArgs[2].num;
// Case: User-specified increment
}else if(loopArgs.length == 4){
loBound = loopArgs[1].num;
incr = loopArgs[2].num;
hiBound = loopArgs[3].num;
// Else: There is a syntax error
}else return ExprInContext(
new Atom( F_Error.SYNTAX, loopArgs.length.to!string ~
" was an incorrect number of loop args.
Expected 3 or 4." ),
eINc.context,
"`for` got an unexpected number of args"
);
// 2. Create a new nested context, bind the counter var
i = loBound;
nuEnv = new Env();
nuEnv.parent = eINc.context;
bind_atom( nuEnv, iVarName, new Atom( loBound ) );
runBlock = ExprInContext(
loopProg,
nuEnv,
"loop body"
);
// 3. LOOP:
while( i <= hiBound ){
// run block in nested context
rtnExpr = block_meaning( runBlock ).expr;
i += incr; // increment
// Store new counter value so that loop body can access it
bind_atom( nuEnv, iVarName, new Atom( i ) );
}
return ExprInContext(
rtnExpr,
eINc.context,
"loop result"
);
};
```
