Re: Compile question

*To*: mathgroup at smc.vnet.net*Subject*: [mg73916] Re: Compile question*From*: dh <dh at metrohm.ch>*Date*: Sat, 3 Mar 2007 00:59:53 -0500 (EST)*References*: <es6d6h$rq1$1@smc.vnet.net>

Hi Ray, if you replace the empty list in the Last If[..] by e.g.: {-1} it works as expected. Why this is so I can only guess. Presumably, a compiled function must always return the same type of expression. And an empty array may be regarded as an empty array of reals. Daniel Ray Koopman wrote: > I've been trying different ways to "walk the list" as suggested in > the recent thread "split again". Here is some uncompiled code that > works as I expected, but the compiled version returns reals instead > of integers. Does anyone know why? > > SeedRandom[2]; z = Table[Random[],{20}] > > {0.238705,0.844529,0.473928,0.421515,0.512692, > 0.0228035,0.529257,0.0507012,0.74907,0.632356, > 0.0725195,0.251276,0.902785,0.672727,0.419794, > 0.512577,0.404555,0.00984124,0.168643,0.50482} > > s4[z_,a_,b_] := Module[{n = Length@z, j = 0, k}, k = n; > Do[If[ z[[i]] >= a, If[ i <= j+b+1, j = i, k = i-1; Break[]]], {i,n}]; > If[ k <= j+b, {}, {j+1,k} ] ] > > s4[z,.7,5] > s4[z,.7,6] > s4[z,.7,7] > > {3,8} > {14,20} > {} > > s4c = Compile[{{z,_Real,1},{a,_Real},{b,_Integer}}, > Module[{n = Length@z, j = 0, k}, k = n; > Do[If[ z[[i]] >= a, If[ i <= j+b+1, j = i, k = i-1; Break[]]], {i,n}]; > If[ k <= j+b, {}, {j+1,k} ] ], > {{n,_Integer},{j,_Integer},{k,_Integer},{i,_Integer}} ]; > > s4c[z,.7,5] > s4c[z,.7,6] > s4c[z,.7,7} > > {3.,8.} > {14.,20.} > {} > >