yet another anagram algorithm, this time in Rust
The text provided by --help.
```
USAGE:
rana [FLAGS] [OPTIONS]
FLAGS: -h, --help Prints help information -C, --no-cache Do not cache partial results (this saves memory and costs speed) -r, --random (Partially) shuffle order of discovery -w, --words-in Returns the set of words composable from the letters in the input phrase -V, --version Prints version information
OPTIONS:
-d, --dictionary
ARGS:
Rana generates all the possible anagrams from a given phrase and dictionary. Note "given some dictionary." Rana does not have a word list built in. You must tell it what words it may use in an anagram. I have made myself such a list out of a list of English words I found on the Internet from which I deleted all the words likely to offend people. By default rana will look in your home directory for a file called .anagrams-dictionary.txt.
In many cases a simple phrase will have hundreds of thousands or millions of anagrams, setting aside permutations. The phrase "rotten apple", for example, with a fairly ordinary dictionary of of 109,217 English words, produces 2695 anagrams. Here are 10:
pone prattle plea portent pole pattern portent pale platter pone planter poet potent paler porn palette pron palette poler patent
Because so many anagrams are available, you are likely to want to focus your search. Rana provides several options to facilitate this.
--words-in
This will list all the words in your dictionary composable from some subset of your phrase.
--exclude
Discard from your word list particular words.
--include
Include only those phrases which include particular words.
--limit
Only provide a sample of this many phrases.
--random
Shuffle the search order over partial results while searching for anagrams. This does not provide a fully random sample of the possible anagrams, since only the results found at any point are shuffled, not all possible results, but this is a decent way to look at a sample of anagrams when the phrase you've fed in has many thousands of results. This is particularly useful when paired with --limit.
Caching and Threads
Rana by default uses as many processing threads as there are cores on your machine. Generally this is what you want, but if you've got a lot of other things going on, you can limit the number of available threads to reduce the load your kernel has to deal with.
Rana also uses a dynamic programming algorithm to reduce the complexity of finding algorithms for large phrases. This is probably unnecessary for short phrases, though rana provides no lower limit. For larger phrases, like the complete alphabet, the cache used by the dynamic programming algorithm may grow so large that the process crashes. If you turn off the cache rana will use a constant amount of memory, though it may take considerably longer to find all anagrams.
Text Normalization
Rana attempts to strip away certain characters from your word list and all other textual input, so it will treat "c-a-t" and " C A T " the same as "cat". Here is the actual code that does this:
pub fn normalize(word: &str) -> String {
word.trim()
.to_lowercase()
.chars()
.filter(|c| c.is_alphabetic())
.collect::<String>()
}
I have not tested what this will do for something like ß or Í. You may want to normalize the text yourself before you give it to rana.
NOTE:
The caching algorithm treats character counts as long base-10 numbers. So, for example, "cat" might be 111 if "c" is 100s, "a" is 10s, and "t" is 1s. Then "cad" might be 1110 -- "d" is 1000s, and there is one of them, but there is no "t", so the 1s place is 0. If you have a phrase, like
"Dhrtaraashtra uvaaca, dharmakshetre kurukshetre samavetaa yuyutsavah"
which has 15 a's, the "a" count has to be represented as 5 -- 15 mod 10 is 5. In other words, there isn't space in the a's column of the number for all the a's in the phrase. It is unlikely that this will ever cause trouble, because for a particular phrase you are unlikely to be encounter two sets of character counts during processing that have different counts but the same code. Also, a phrase this size will consume so much cache space that the process will probably crash before you encounter this collision.
Another consideration with caching is that this scheme can only accommodate alphabets up to 38 characters in size. ```
An example use:
~ $ rana eat
eat
a et
eta
ate
tea
This is not yet up on crates.io. To install it you will need to install the
nightly version of Rust (I believe), clone this project or copy it to your
machine, and run cargo build --release in its directory. This will produce an
executable called target/release/rana. To use the executable you will
need a word list. I have not checked mine in. You can find word lists on-line if
you simply search for "word list". The list will need to have all the forms you
are interested in. Rana cannot infer "cats" from "cat", much less "brought"
from "bring".
I have made many variants of this anagram algorithm. This is the first in Rust. It is more efficient and faster than any of the previous versions. I cannot say that this is particularly good or idiomatic Rust. It is the fist significant bit of Rust I've ever written. To the extent that this is good Rust, the credit is entirely due to @TurkeyMcMac, who knows Rust much better than I do and could generally tell me when I was doing something particularly stupid.