GEnerator Expressions in julialang

generator_expressions_study.jl

# Generator Expressions
# - comprehensions can also be written without the enclosing square brackets, producing an object known as a generator 
# - can be iterated to produce values on demand, instead of allocating an array and storing them in advance
# - Generators are implemented via inner functions.
# - simple example
(1/n^2 for n=1:1000)
# - collect
collect(1/n^2 for n=1:1000)
# - the following expression sums a series without allocating memory
map(tuple, (1/(i+j) for i=1:2, j=1:2), [1 3; 2 4])
# is the same logic as
map(tuple, [0.5 0.33333; 0.33333 0.25], [1 3; 2 4])
# ranges in generators and comprehensions can depend on previous ranges by writing multiple for keywords
[(i,j) for i=1:3 for j=1:i]
# Generated values can be filtered using the if keyword
[(i,j) for i=1:3 for j=1:i if i+j == 4]