Jensen’s device

• Why define Call by Name?

• Highly expressive

  • At least based on this one classic example!

real proc SUM (k, low, up, ak);

value low, up;

integer k, low, up; real ak;

begin real s;

s := 0;

for k := low step 1 until up do

s := s + ak; sum := s

end;

• sum(i, 1, m, A[i])

• sum(i, 1, m, sum(j, 1, n, B[i,j]))

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