Icon Analyst 52 -- Supplementary Material

Last updated February 6, 1999

A Weaving Language

Weaving Procedures

Pattern Forms Revisited

Conversion Procedure

Answers to Quiz on Structures

1. False. L[0] is an attempt to reference an element beyond the end of L, which fails.

2. True.

3. They both produce the same results, but the first leaves L unchanged, while the second removes all its elements, leaving it empty.

4. It adds a null-valued element to the right end of L.

5. They all leave L unchanged, although some differ in intermediate steps.

6. L := sort(set(L)).

7. True.

8. False.

9. False.

10. False. If R has a field named center, they produce the same results, but if R doesn’t have a field named center, R.center causes a run-time error, while R["center"] fails.

11. True.

12. True.

13. False.

14. False; the order is unpredictable but not random.

15. *sort(S).


procedure elim_str(S)

every x := !S do
if type(x) == "string" then delete(S, x)

return S


17. set(R), set(S), set(T), and list(S) cause run-time errors. table(S) creates a table whose default value is S.

18. True.

19. False in general.

procedure keyset(T)

S := set()

every insert(S, keys(T))

return S


21. Values can be obtained from keys, as in T[key(T)]. The converse is not true.

22. True, although this is a property of the implementation and not specified in the language.

23. False. Although there is no language or implementation limit on the number of elements in a table, it must fit in memory, which is limited.

Graphics Corner -- Transparency

Figure 1. The Affect of Transparency

Figure 2. Unicorn Silhouette

Figure 3. A Numerical Carpet

Figure 4. Unicorn Adorned with a Carpet

Figure 5. Other Unicorn Adornments

Figure 6. The Images for Masks

Figure 7. Shuttering the Unicorn

Animation -- Mutable Colors

Figure 1. Marquee Layout

Figure 2. Successive Marquee Images

Marquee Animation

Figure 3. Path Layout

Figure 4. Snapshots of the Worm

Worms Animation

Figure 5. An Expanding Ring

Ring Animation

Figure 6. Revolving Rotors

Rotors Animation

Figure 7. Revolving Color Wheel

Color Wheel Animation

From the Library -- PostScript Graphics

Figure 1. Screen Image

Figure 2. Enlarged Screen Image

Figure 4. Color Artifact in Reversible Drawing
As the article points out, we can’t show the reolution independence of PostScript images in a bit-mapped medium like this Web page. Here are links to the PostScript files in case you want to print them yourself.

Figure 3. PostScript Image

Figure 4. Enlarged PostScript

Orbit animation (17k)
Awake animation (102k)
Graphics Corner -- Transparency

Figure 5. Pixel Rendering

Figure 6. PostScript Rendering

Figure 1. Black and White Queens
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