§16.9. Blank rows
There is no difficulty about entirely blank rows: or rather, the only difficulty is once again that they are boring to type out. We can avoid the necessity by appending "with ... blank rows" at the foot of the table:
Element | Symbol | Atomic number | Atomic weight |
"Hydrogen" | "H" | 1 | a number |
"Iron" | "Fe" | 26 | -- |
"Zinc" | "Zn" | 30 | -- |
"Uranium" | "U" | 92 | -- |
with 3 blank rows |
(These words cannot be placed in between rows, but only at the bottom.) And indeed the table can start out completely empty:
Element (text) | Symbol (text) | Atomic number (a number) | Atomic weight (a number) |
with 92 blank rows |
Blank rows are useful because they enable us to add new data to a table. In effect, they are invisible when not used. A repeat loop like
repeat through Table 3:
...
automatically skips blank rows, so it would initially do nothing at all. Similarly, choosing a "random" row will never choose a blank one.
A convenient way to test if a table contains non-blank rows is to use the built-in adjectives "empty" and "non-empty". So:
if the Undiscovered Periodic Table is empty, ...
tests whether all of its rows are blank; if even one cell contains a value then the table is "non-empty".
|