Canon Camera, Hackers Manual

Page: 106 / 257

5.4 Lua primer
97
for i = 1,10,3 do
print(i)
end
would print the values 1, 4, 7, 10.
A second form of the for statement—called the generic for state-
ment—allows iteration over a series of values, such as the elements of a
table. Using the built-in function
ipairs() , we can write:
disp_table = { ' info ' , ' no_info ' , ' off ' , ' electronic_viewfinder ' }
for i,v in ipairs(disp_table) do
print(i,v)
end
This results in the output:
1 info
2 no_info
3 off
4 electronic_viewfinder
The same is possible for dictionary tables that are accessible via keywords.
Instead of
ipairs() , the function pairs() is used in this case:
t = {info = 0, no_info = 1, off = 2, electronic_viewfinder = 3}
for key,value in pairs(t) do
print(key,value)
end
The result of this script would be:
electronic_viewfinder 3
off 2
info 0
no_info 1
Note that in this case the order in which the values are obtained cannot be
predicted.
In addition to the various flavors of the for statement, Lua also features
a
while
statement and a
repeat
statement. The latter replaces the
do...
until construct found in uBasic .