Migration notice: The git repository for this project has moved to https://codeberg.org/penguinite/expect, this link will still work but it will not contain any new updates.
Rust-style expect procedures for Nim.
Note: expect only works with the Option object from std/options
Proper documentation on how to use expect can be found here
Install with nimble: nimble install expect or nimble install https://github.com/penguinite/expect.git
Add it to your nimble dependencies:
require "expect"
# OR
require "https://github.com/penguinite/expect.git"
And now you can import it:
import expect
And here is how you use it:
# Let's say we are parsing a Token tree.
# Of course, this is probably different from how you'd actually use expect()
# This is just a demonstration.
type
TokenKind = enum
Symbol, Sign
# Some random data
# Notice how some parts of it are missing?
# We can use expect to filter out any unknown tokens when we parse it.
let data: seq[Option[TokenKind]] = @[
some(Symbol), some(Symbol), none(TokenKind),
]
for i in data:
# Here we use expect as a kind of safety mechanism.
# When expect() encounters an unknown token, it will quit the program and print the error message. "Unknown token encountered!"
discard i.expect("Unknown token encountered!")
var count = 0
for i in data:
inc count
# We can also use our own procedure instead of simply having expect() quit by itself.
# This allows for even more flexibility, you can use your own logging procedures,
# or maybe run a failsafe procedure, or anything else you'd like.
#
# The possibilities are endless, except, we can't pass any data to these procs
#
5C3C
so they can only access variables in their scope.
proc log() =
echo "Unknown token encountered at position ", count, "!"
# Here we tell expect to run the log() procedure instead of printing a message and quitting.
# This will print "Unknown token encountered at position 3!" and simply continue parsing
discard i.expect(log)