On 29/12/2021 19:33, Andrey Tarasevich wrote:
> On 12/29/2021 9:49 AM, Bart wrote:

>> 2) Nothing wrong with using 'float' when it's appropropriate. Many
>> libraries eg. OpenGL make extensive use of float.
>
> That's just emphasizes my the point. The main purpose of "small" types,
> like `float`, `short`, char as plain integer, bit-fields etc. is to save
> memory in quantitatively massive data structures.
>
> That's exactly what OpenGL is intended to work with: massive amounts of
> geometric data. That's why it opts for `float` Everything else is just a
> consequence of that.

It has to give acceptable results. Presumably float's accuracy is
sufficient for that. Using less memory, and being somewhat faster, are
bonuses.

>> and in one place for quick reference.
>
> Piling up all variable declarations in one place makes for much slower
> reference: first, one has has to find the pile, then one has to sift
> through the pile.
>
> Local declarations are always instantly visible,

That's the problem! If trying to appreciate the algorithm, the types and
attributes of the variables are secondary.

Also, the type is only applied to the first occurence. You see
'interest' being used on a subsequent; what type is it? You glance at
the top of the function - it's not there! You have to scan backwards
from where you are until you encounter a matching declaration.

But then, if 'interest' /was/ declared at the top, now you are wasting
type doing that scan.

(This is a simple program. Have a look at something like the amalgmated
source file of sqlite3.c, where they really take your style on board.

You also have to contend with names with appear identical but have
subtle differences, or the same name declared more than once in the same
function. If you miss the first declaration on that backwards scan, you
may end up at the wrong one.

Look at the two declarations of pKeyInfo in this extract:

if( pPart || pOrderBy ){
int nPart = (pPart ? pPart->nExpr : 0);
int addrGoto = 0;
int addrJump = 0;
int nPeer = (pOrderBy ? pOrderBy->nExpr : 0);

if( pPart ){
int regNewPart = reg + pMWin->nBufferCol;
KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pPart, 0, 0);
addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPart,
pMWin->regPart,nPart);
sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
addrJump = sqlite3VdbeAddOp3(v, OP_Jump, addr+2, 0, addr+2);
VdbeCoverageEqNe(v);
windowAggFinal(pParse, pMWin, 1);
if( pOrderBy ){
addrGoto = sqlite3VdbeAddOp0(v, OP_Goto);
}
}

if( pOrderBy ){
int regNewPeer = reg + pMWin->nBufferCol + nPart;
int regPeer = pMWin->regPart + nPart;

if( addrJump ) sqlite3VdbeJumpHere(v, addrJump);
if( pMWin->eType==TK_RANGE ){
KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse,
pOrderBy, 0, 0);
addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPeer, regPeer,
nPeer);
sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
addrJump = sqlite3VdbeAddOp3(v, OP_Jump, addr+2, 0, addr+2);
VdbeCoverage(v);
}else{
addrJump = 0;
}
windowAggFinal(pParse, pMWin, pMWin->eStart==TK_CURRENT);
if( addrGoto ) sqlite3VdbeJumpHere(v, addrGoto);
}

Note that I've helped you by isolating the lines with both declarations,
but some functions are considerably longer, such as one of 750 lines
with 3 versions of "pPk".

Yet another delight is a 7000-line function, which uses names such as
"pcx" and "pCx" (with different types), or "pVtab" (of type sqlite_vtab)
and "pVTab" (of type VTABLE!).

All the 300+ locals in this function are listed below. Not all identical
names have the same type (eg. 'len' exists as 'long' and also 'int').

If all were listed at the top, there would necessarily be fewer as you
couldn't have duplicates (some will be labels), but if sorted like this
must surely be easier to find than scanning 7000 lines of dense code.

----------------------------------------------

(Sorry the types are not in proper C syntax. Names with void types are
labels.)

abort_due_to_error void
abort_due_to_interrupt void
aEQb [6]const uchar
affinity schar
aFlag [2]const ushort
aGTb [6]const uchar
alreadyExists int
aLTb [6]const uchar
aMem ref struct sqlite3_value
and_logic [9]const uchar
aOffset ref uint
aOp ref struct VdbeOp
apArg ref ref struct sqlite3_value
apArg ref ref struct sqlite3_value
aPermute ref int
aRes [3]int
arithmetic_result_is_null void
aRoot ref int
aZero [16]uchar
azType [4]const ref const schar
bIntint schar
bRev int
c int
c int
check_for_interrupt void
cnt int
cnt int
compare_op void
Compiling sqlite3.c to sqlite3.exe
db ref struct sqlite3
desiredAutoCommit int
encoding uchar
eNew int
eOld int
eqOnly int
exists int
file_format int
flags ushort
flags1 ushort
flags3 ushort
fp_math void
i int
i int
i int
i int
i int
i int
i int
i int
i int
i int
iA llong
iA llong
iAddr uint
iB llong
iB llong
iCompare int
iCookie int
iDb int
iDb int
iDb int
iDb int
idx int
ii int
ii int
iKey llong
iKey ullong
iMeta int
iMeta int
iMoved int
initData struct (ref struct sqlite3 db,ref ref
schar pzErrMsg,int iDb,int rc,uint mInitFlags)
iPrior uint
iQuery int
iRollback int
iSavepoint int
iSet int
isLegacy int
isNotInt int
isSchemaChange int
isTransaction int
isWriteLock uchar
j int
jump_to_p2 void
jump_to_p2_and_check_for_interrupt void
len int
len uint
n int
n int
n int
n int
n int
n uint
nArg int
nArg int
nByte int
nByte llong
nByte llong
nChange int
nData ullong
nEntry llong
nErr int
newMax uint
next_tail void
nField int
nField int
nField int
nHdr int
nKeyCol int
nMem int
nName int
no_mem void
nProgressLimit uint
nRoot int
nullFlag ushort
nVarint int
nVmStep uint
nZero llong
oc int
offset64 ullong
On line: 140
op uchar
op_column_corrupt void
op_column_out void
op_column_read_header void
open_cursor_set_hints void
opflags int
or_logic [9]const uchar
origFlags ushort
p ref struct Vdbe
p1 int
p1 int
p1 int
p1 int
p2 int
p2 int
p2 int
p2 int
pArgc ref struct sqlite3_value
pBt ref struct Btree
pBt ref struct Btree
pBt ref struct Btree
pBt ref struct Btree
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pC ref struct VdbeCursor
pCaller ref struct VdbeOp
pcDest int
pColl ref struct CollSeq
pCrsr ref struct BtCursor
pCrsr ref struct BtCursor
pCrsr ref struct BtCursor
pCrsr ref struct BtCursor
pCrsr ref struct BtCursor
pCrsr ref struct BtCursor
pCrsr ref struct BtCursor
pCrsr ref struct BtCursor
pCtx ref struct sqlite3_context
pCtx ref struct sqlite3_context
pCtx ref struct sqlite3_context
pCtx ref struct sqlite3_context
pCur ref struct VdbeCursor
pCur ref struct VdbeCursor
pCur ref struct VdbeCursor
pCur ref struct VdbeCursor
pCur ref struct VdbeCursor
pcx int
pCx ref struct VdbeCursor
pCx ref struct VdbeCursor
pCx ref struct VdbeCursor
pCx ref struct VdbeCursor
pData ref struct sqlite3_value
pData0 ref struct sqlite3_value
pDb ref struct Db
pDb ref struct Db
pDb ref struct Db
pDest ref struct sqlite3_value
pDest ref struct sqlite3_value
pEnd ref struct sqlite3_value
pFrame ref struct VdbeFrame
pFrame ref struct VdbeFrame
pFrame ref struct VdbeFrame
pFrame ref struct VdbeFrame
pFrame ref struct VdbeFrame
pFree ref struct UnpackedRecord
pgno int
pgno int
pIdxKey ref struct UnpackedRecord
pIn ref struct sqlite3_value
pIn1 ref struct sqlite3_value
pIn2 ref struct sqlite3_value
pIn3 ref struct sqlite3_value
pKey ref struct sqlite3_value
pKeyInfo ref struct KeyInfo
pKeyInfo ref struct KeyInfo
pKeyInfo ref struct KeyInfo
pLast ref struct sqlite3_value
pMem ref struct sqlite3_value
pMem ref struct sqlite3_value
pMem ref struct sqlite3_value
pMem ref struct sqlite3_value
pMem ref struct sqlite3_value
pMem ref struct sqlite3_value
pModule ref struct sqlite3_module
pModule ref struct sqlite3_module
pModule ref struct sqlite3_module
pModule ref struct sqlite3_module
pModule ref struct sqlite3_module
pModule ref struct sqlite3_module
pName ref struct sqlite3_value
pnErr ref struct sqlite3_value
pNew ref struct Savepoint
pOp ref struct VdbeOp
pOrig ref struct VdbeCursor
pOut ref struct sqlite3_value
pPager ref struct Pager
pProgram ref struct SubProgram
pQuery ref struct sqlite3_value
pRec ref struct sqlite3_value
pReg ref struct sqlite3_value
pRt ref struct sqlite3_value
pSavepoint ref struct Savepoint
pTab ref struct Table
pTab ref struct Table
pTabCur ref struct VdbeCursor
pTmp ref struct Savepoint
pVar ref struct sqlite3_value
pVCur ref struct sqlite3_vtab_cursor
pVCur ref struct sqlite3_vtab_cursor
pVtab ref struct sqlite3_vtab
pVtab ref struct sqlite3_vtab
pVtab ref struct sqlite3_vtab
pVtab ref struct sqlite3_vtab
pVtab ref struct sqlite3_vtab
pVtab ref struct sqlite3_vtab
pVtab ref struct sqlite3_vtab
pVTab ref struct VTable
pX ref struct Btree
pX ref struct sqlite3_value
r struct (ref struct KeyInfo pKeyInfo,ref
struct sqlite3_value aMem,ushort nField,schar default_rc,uchar
errCode,schar r1,schar r2,uchar eqSeen)
r struct (ref struct KeyInfo pKeyInfo,ref
struct sqlite3_value aMem,ushort nField,schar default_rc,uchar
errCode,schar r1,schar r2,uchar eqSeen)
r struct (ref struct KeyInfo pKeyInfo,ref
struct sqlite3_value aMem,ushort nField,schar default_rc,uchar
errCode,schar r1,schar r2,uchar eqSeen)
r struct (ref struct KeyInfo pKeyInfo,ref
struct sqlite3_value aMem,ushort nField,schar default_rc,uchar
errCode,schar r1,schar r2,uchar eqSeen)
rA double
rB double
rc int
res int
res int
res int
res int
res int
res int
res int
res int
res int
res int
res int
res int
res int
res2 int
resetSchemaOnFault uchar
rowid llong
rowid llong
sContext struct (ref struct sqlite3_value pOut,ref
struct FuncDef pFunc,ref struct sqlite3_value pMem,ref struct Vdbe
pVdbe,int iOp,int isError,uchar skipFlag,uchar argc,[1]ref struct
sqlite3_value argv)
seek_not_found void
seekResult int
serial_type uint
sMem struct (union MemValue u,ushort
flags,uchar enc,uchar eSubtype,int n,ref schar z,ref schar zMalloc,int
szMalloc,uint uTemp,ref struct sqlite3 db,ref proc(ref void)void xDel)
sMem struct (union MemValue u,ushort
flags,uchar enc,uchar eSubtype,int n,ref schar z,ref schar zMalloc,int
szMalloc,uint uTemp,ref struct sqlite3 db,ref proc(ref void)void xDel)
sz llong
t ref void
t uint
takeJump int
too_big void
type1 ushort
type2 ushort
uA ullong
v llong
v llong
v1 int
v2 int
val llong
vdbe_return void
vfsFlags const int
vtabOnConflict uchar
wrFlag int
x llong
x ref proc(ref void,ref const schar)void
x struct (ref const void pKey,llong
nKey,ref const void pData,ref struct sqlite3_value aMem,ushort nMem,int
nData,int nZero)
x struct (ref const void pKey,llong
nKey,ref const void pData,ref struct sqlite3_value aMem,ushort nMem,int
nData,int nZero)
z ref const schar
z ref schar
z ref schar
z ref schar
zAffinity ref const schar
zAffinity ref schar
zData ref const uchar
zDb ref const schar
zDb ref const schar
zEndHdr ref const uchar
zFilename ref const schar
zHdr ref const uchar
zMaster ref const schar
zName ref schar
zNewRecord ref uchar
zSql ref schar
zTab ref const schar
zTrace ref schar