kro(a,q) vs. issquare()

[John Cremona <John.Cremona@nottingham.ac.uk>]

Why is kro(a,q) very much faster (about 3 times) than issquare for
testing modular squares?

Example:  q=103; a=34; aa=Mod(a,q);

Now 
          for(j=1,10^6,t=issquare(aa));t
takes 9,839ms, while
          for(j=1,10^6,t=kro(a,q));t
takes only 3,670ms.

If it is because issquare() is also computing the root (returned through
an optional second argument) then there is still something wrong since
that does not work with this type:  issquare(aa,&b) gives the error
message   ***   not an integer argument in an arithmetic function

John

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