RB strings are not mutable...
When you call " s = s + str(i) " a new string is created in memory,
the value of the old string plus the new string are added together an
placed in the new string, and then the old string is taken out of
memory.
Each iteration of this loop will therefore be a little longer than
the last, as the string slowly winds it's way up to 50,000 characters
long.
Array's are much faster than strings for appends, but I defy you to
do an instr or countfields operation on one of your fast strings....
Different horses for different courses Kem....
- Tom
On 12/02/2007, at 4:17 PM, Kem Tekinay wrote:
I know this has probably been done to death, but I wanted emphasize
how slow
strings are in REALbasic for appends. Consider this code, for example:
for i as integer = 1 to 50000
s = s + str( i )
next i
This takes 17 seconds to run in a compiled app on a PowerMac G5
dual-2.5
GHz.
Meanwhile, I took about an hour to create a custom class called
FastString
that uses an array to hold the parts of the string. By defining the
Operator_Add and Operator_Convert methods, I can change s above from a
string to a FastString, and the exact same code takes 0.1 seconds!
If I
rewrite the code to use a method within FastString, it takes half
that:
for i as integer = 1 to 50000
s.Append( str( i ) )
next i
OK, so part of this is bragging, but the more serious question is,
if I
could do this in an hour, why can't RB use the same behavior in its
native
strings?
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