Initial Commit

Code/13.fileIO.jl

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+
+# File IO is really similar to how it would be done in python and C.
+
+io = open("test.txt", "w") # Opens test.txt for writing
+write(io, "Hello World!") # writes a string to it
+close(io) # closes the file
+
+# However the more appropriate way to do it would be more similar to
+# Python's "with" statement. This encloses the file handling in a code block
+# and automatically closes the filestream and does cleanup if anything goes
+# wrong.
+open("test.txt", "w") do io
+    write(io, "Hello\nWorld!")
+end
+
+# The do-syntax here is really just syntactical sugar for giving the
+# open() function a function as an argument
+
+# The following syntax is effectively what the do-syntax above does.
+# Create a function taking in a single argument with the file-handling code
+function f(io)
+    write(io, "Hello\nWorld!")
+end
+
+# call the open function with this function as the first parameter
+open(f, "test.txt", "w")
+
+# This makes for some really clean and safe file handling syntax.
+s = open("test.txt", "r") do io
+    collect(eachline(io))
+end
+display(s)
+
+# for simple functions as the one above it is possible to just pass
+# the the function directly in without using the do-syntax
+# for a really compact one line function call
+# The ∘ symbol is function composition (from mathematics)
+s = open(collect ∘ eachline, "test.txt", "r")
+display(s)