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## [Reduce-algebra-developers] A crash when using modular arithmetic

 [Reduce-algebra-developers] A crash when using modular arithmetic From: Rainer Schöpf - 2012-10-23 16:36:27 ```Try this: on modular; setmod 2; % This causes nil to be called as function sqrt(1-x^2); The crash happens when sqfrf tries a square free factorization of x^2-1, by differentiating it and computing the gcd. But with setmod 2, the derivative 2*x is simplified to 0. It is not so difficult to avoid the crash, but I'm not sure how the case should be handled. Some more fun: on modular; setmod 11; int(sqrt(1-x^2),x,0,1); Rainer ```

 [Reduce-algebra-developers] A crash when using modular arithmetic From: Rainer Schöpf - 2012-10-23 16:36:27 ```Try this: on modular; setmod 2; % This causes nil to be called as function sqrt(1-x^2); The crash happens when sqfrf tries a square free factorization of x^2-1, by differentiating it and computing the gcd. But with setmod 2, the derivative 2*x is simplified to 0. It is not so difficult to avoid the crash, but I'm not sure how the case should be handled. Some more fun: on modular; setmod 11; int(sqrt(1-x^2),x,0,1); Rainer ```