| Matrix2d m; m << 1,2,3,4; |
| Matrix2d n; |
| n = (m*m).lazy(); // if we did "n = m*m;" then m*m would first be evaluated into |
| // a temporary, because the Product expression has the EvalBeforeAssigningBit. |
| // This temporary would then be copied into n. Introducing this temporary is |
| // useless here and wastes time. Doing "n = (m*m).lazy();" evaluates m*m directly |
| // into n, which is faster. But, beware! This is only correct because m and n |
| // are two distinct matrices. Doing "m = (m*m).lazy();" would not produce the |
| // expected result. |
| cout << n << endl; |