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I've used List.exists( ), i woudl like to know if there is an equivalent for Db.

If i have a function f(e) : bool, i would like to know if there is at least one element e, with f(e) -> true. Currently i use the Db.intmap_fold_range( ), but it iterates over all the Db, whereas it would be better for performances to stop at the first return true.

trecouvr
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1 Answers1

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I suppose your DB is an IntMap if you can use Db.intmap_fold_range.

This is a sample code : 

// Testing function
f(key, val) = key == 42

// Check existence in "mymap"
res = IntMap.exists(f, /mymap)

If you look at the source code, you can see that it is implemented for folding only on the necessary elements :) (File: stdlib/core/map/map.opa)

akoprowski
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Fred
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  • Hi, don't you think IntMap.exists(f, /mymap) will create a new map from the Db before to perform ? I've heard that using Map functions on Db is unperformant because a new map is created each time (it's for this reason we use Db.intmap_fold_range( )) – trecouvr Jul 14 '11 at 10:29