User Tools

Site Tools


caveat

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

caveat [2014/05/30 11:49] (current)
Line 1: Line 1:
 +
 +You may have noticed that in the original, mathematical equation at the top of the page, there were **bounds** on the summation, <​latex>​$\sum_{k=1}^{i-1}$</​latex>​. ​ In the Alphabets program we wrote, we did not include these bounds. ​ In this equation, this is safe, for a rather subtle reason (which will be clearer when you know more about Alpha). ​ In general, it is always safe to include these bounds explicitly in your program by making the reduction body a RestrictExpression to explicitly specify the range of indices where the expression inside the reduction is defined, as shown below.
 +
 +<sxh alphabets; gutter:​true>​
 +U[i,j] = case
 +   ​{|1==i} : A[i,j];
 +   ​{|1<​i} : A[i,j] - reduce(+, [k], {|1<​=k<​i} : L[i,​k]*U[k,​j]);​
 +esac;
 +</​sxh>​
  
caveat.txt ยท Last modified: 2014/05/30 11:49 (external edit)