Bug in NIntegrate[]?

*To*: mathgroup at smc.vnet.net*Subject*: [mg126879] Bug in NIntegrate[]?*From*: GS <vokaputs at gmail.com>*Date*: Fri, 15 Jun 2012 03:41:03 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

I define the function f[x] as follows: f[x_] := 0 /; x < 0 || x > 1; f[x_] := 1 It is zero outside of the interval [0,1]. This can be verified by plotting Plot[f[x], {x, -1, 2}] Now I integrate it from -1 to 2: In[270]:= NIntegrate[f[x], {x, -1, 2}] Out[270]= 3. The result should be 1, but it is 3. Clearly Mathematica ignores the fact that f[x] is zero outside of [0,1]. This caused a lot of headache for me recently when I encountered such behavior in one of my research code. GS

**Follow-Ups**:**Re: Bug in NIntegrate[]?***From:*Andrzej Kozlowski <akozlowski@gmail.com>

**Re: Bug in NIntegrate[]?***From:*Sseziwa Mukasa <mukasa@gmail.com>

**Re: Bug in NIntegrate[]?***From:*Bob Hanlon <hanlonr357@gmail.com>

**Re: Bug in NIntegrate[]?***From:*Tomas Garza <tgarza10@msn.com>

**Re: Bug in NIntegrate[]?***From:*Gerry Flanagan <gvflan@midcoast.com>