Hi guys,
Collection defines #sum:, #detectSum: and #sumNumbers:, all of which accomplish
the same (in principal) but with subtle differences:
#sum:
- uses #inject:into: with #anyOne as the injected element and will thus fail
for empty collections
#detectSum:
- uses “nextValue + sum” instead of “sum + nextValue” which makes it a lot
slower when dealing with large numbers (primitive fails and number conversion
is necessary)
#sumNumbers:
- same as #sum but doesn’t fail for empty collections. Only good for numbers
though.
Benchmarks:
[ 100 timesRepeat: [ (1 to: 1000000) sum: #yourself ] ] timeToRun 18062
[ 100 timesRepeat: [ (1 to: 1000000) detectSum: #yourself ] ] timeToRun 42391
[ 100 timesRepeat: [ (1 to: 1000000) sumNumbers: #yourself ] ] timeToRun 18096
Can we settle for a single implementation? Such as (modified from #sumNumbers:):
newSum: aBlock
^ self
inject: (self
ifEmpty: [ 0 ]
ifNotEmpty: [ self anyOne ])
into: [ :sum :each | sum + (aBlock value: each) ]
This implementation combines the best of the three implementations I think.
Benchmark:
[ 100 timesRepeat: [ (1 to: 1000000) newSum: #yourself ] ] timeToRun 17955
BTW, there is also the message #sum, which suffers from the same problem as
#sum: (the implementation is basically a copy). #sum could be implemented as
sum
^ self sum: [ :x | x ]
As for the name for the new method, I suggest #sum:.
Cheers,
Max
