Marking Tests

Way back in section 1.4 you wrote a dfn to convert test scores into letter values.

You were led to produce some function or expression similar to the following:

      Grade←{'FDCBA'[+/⍵∘.>80 70 60 50 0]}
      Grade 95 65 92 77

This is an array-oriented solution to this problem. However, if a human was manually grading test scores, they might take one scored paper at a time and decide on which letter grade to write by reading each score.

Procedural psuedocode:

scores = 93,85,45,10,70,16,93,63,41,7,95,45,76
For each score in scores:
  If score is greater than 80:
    Write "A"
  Else If score is greater than 70:
    Write "B"
  Else If score is greater than 60:
    Write "C"
  Else If score is greater than 50:
    Write "D"
  Else
    Write "F"

Control Structures in Dyalog are keywords beginning with a : colon.

      :If :OrIf :AndIf :ElseIf :Else :EndIf
      :For :In :EndFor
      :While :EndWhile
      :Repeat :Until

Exit from a loop before it is finished using the :Return keyword.

Tasks

  1. Translate the pseudocode above into a tradfn called Grade2 using control stuctures.

  2. Rewrite the Grade function again as either a dfn or a tradfn called Grade3 which uses the interval index function (dyadic ⍸).

  3. Use the ]runtime user command to compare the computation time for each of the three grading functions.

           ]runtime -c "Grade 10×⍳10" "Grade2 10×⍳10" "Grade3 10×⍳10"