commit bdd1dcea065a87ba2920db41382179c54c27818b
Author: Sander Hautvast <sander.hautvast@ing.com>
Date:   Thu Apr 28 16:18:17 2022 +0200

    first commit: padding, and draft for ngrams, probably useless

diff --git a/.idea/.gitignore b/.idea/.gitignore
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index 0000000..13566b8
--- /dev/null
+++ b/.idea/.gitignore
@@ -0,0 +1,8 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml
diff --git a/src/lib.rs b/src/lib.rs
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index 0000000..7c30d21
--- /dev/null
+++ b/src/lib.rs
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+mod edit_distance;
+mod ngrams;
+mod lm;
+mod util;
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diff --git a/src/lm/mod.rs b/src/lm/mod.rs
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+++ b/src/lm/mod.rs
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+mod preprocessing;
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diff --git a/src/lm/preprocessing.rs b/src/lm/preprocessing.rs
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index 0000000..e1e6a14
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+++ b/src/lm/preprocessing.rs
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+/// Pads a sequence of words with defaults; prepends "<s>" and appends "<s>"
+///
+/// sentence: sequence of words, tokens, to pad, in the form of an Iterator of string slices.
+/// n: the n in n-grams; so for bigrams set to 2, etc
+pub fn pad_both_ends<'a>(text: impl Iterator<Item=&'a str> + 'static, n: usize) -> impl Iterator<Item=&'a str> {
+    crate::util::Padder::new(Box::new(text), true, "<s>", true,"</s>", n)
+}
+
+
+
+
diff --git a/src/ngrams.rs b/src/ngrams.rs
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--- /dev/null
+++ b/src/ngrams.rs
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+use std::cmp::Ordering;
+use std::collections::BTreeMap;
+
+#[derive(Debug, Eq, Ord)]
+pub struct NGram(Vec<&'static str>);
+
+impl NGram {
+    pub fn new(elements: Vec<&'static str>) -> Self {
+        Self {
+            0: elements
+        }
+    }
+
+    pub fn new_bigram(element1: &'static str, element2: &'static str) -> Self {
+        Self {
+            0: vec![element1, element2]
+        }
+    }
+
+    pub fn new_trigram(element1: &'static str, element2: &'static str, element3: &'static str) -> Self {
+        Self {
+            0: vec![element1, element2, element3]
+        }
+    }
+
+    pub fn tail(&self) -> Self {
+        Self {
+            0: self.0[1..].to_vec()
+        }
+    }
+
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    pub fn get(&self, index: usize) -> &'static str {
+        unsafe {
+            self.0.get_unchecked(index)
+        }
+    }
+}
+
+impl PartialEq for NGram {
+    fn eq(&self, other: &Self) -> bool {
+        if self.len() != other.len() {
+            return false;
+        } else {
+            for (i, element) in self.0.iter().enumerate() {
+                if *element != other.get(i) {
+                    return false;
+                }
+            }
+        }
+
+        true
+    }
+}
+
+impl PartialOrd for NGram {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        if self.eq(other) {
+            Some(Ordering::Equal)
+        } else {
+            for (i, element) in self.0.iter().enumerate() {
+                if let Some(ordering) = element.partial_cmp(&other.get(i)) {
+                    if ordering != Ordering::Equal {
+                        return Some(ordering);
+                    }
+                }
+            }
+            Some(Ordering::Equal)
+        }
+    }
+}
+
+pub struct Model {
+    word_counts: BTreeMap<&'static str, u32>,
+    ngram_counts: BTreeMap<NGram, u32>,
+}
+
+impl Model {
+    pub fn calc_digrams(corpus: Vec<Vec<&'static str>>) -> Self {
+        let mut word_counts = BTreeMap::new();
+        let mut ngram_counts = BTreeMap::new();
+        for sentence in corpus {
+            for word in sentence.iter() {
+                let count = word_counts.entry(*word).or_insert(0);
+                *count += 1;
+            }
+
+            for i in 0..sentence.len() - 1 {
+                let ngram = NGram::new(vec![sentence[i], sentence[i + 1]]);
+                let count = ngram_counts.entry(ngram).or_insert(0);
+                *count += 1;
+            }
+        }
+        Self {
+            ngram_counts,
+            word_counts,
+        }
+    }
+
+    // only tested for 2-grams, and that's only happy cases
+    pub fn p(&self, ngram: NGram) -> Option<f64> {
+        // let mut probability = (*self.word_counts.get(ngram.get(0)).unwrap() as f64) / self.word_counts.len() as f64;
+        //
+        //
+        // for index in 0..ngram.len() - 1 {
+        //     println!("{}", probability);
+        //
+        //
+        //
+        //     println!("{}", ng_p);
+        //     probability = ng_p * probability;
+        // }
+        // println!("{}", probability);
+        // Some(probability)
+        None
+    }
+
+    fn p_ngram(&self, ngram: NGram, intermediate: f64) -> f64 {
+        // for index in 0..ngram.len() - 1 {
+        //     self.ngram_counts.get(&ngram)
+        //         .map(|count| (*count as f64) / (self.word_counts[ngram.0.get(0).unwrap()] as f64)).unwrap()
+        // }
+        //
+        // if ngram.len() > 2 {
+        //     println!("{}", intermediate);
+        //     intermediate * self.pp(ngram.tail(), intermediate) //TODO
+        // } else {
+        //     self.ngram_counts.get(&ngram)
+        //         .map(|count| (*count as f64) / (self.word_counts[ngram.0.get(0).unwrap()] as f64)).unwrap() //TODO
+        // }
+        0.0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_create_model() {
+        let corpus = vec![
+            vec!["<s>", "I", "am", "Sam", "</s>"],
+            vec!["<s>", "Sam", "I", "am", "</s>"],
+            vec!["<s>", "I", "do", "not", "like", "eggs", "and", "ham", "</s>"],
+        ];
+
+        let model = Model::calc_digrams(corpus);
+
+        // assert_eq!(model.p(NGram::new(vec!["<s>", "I"])), Some(0.6666666666666666_f64));
+        // assert_eq!(model.p(NGram::new(vec!["Sam", "</s>"])), Some(0.5_f64));
+        // assert_eq!(model.p(NGram::new(vec!["<s>", "Sam"])), Some(0.33333333333333333_f64));
+        // assert_eq!(model.p(NGram::new(vec!["am", "Sam"])), Some(0.5_f64));
+        // assert_eq!(model.p(NGram::new(vec!["I", "am"])), Some(0.6666666666666666_f64));
+
+        println!("{:?}", model.p(NGram::new(vec!["I", "am", "Sam"])));
+    }
+
+    #[test]
+    fn test_ngram_eq() {
+        let n1 = NGram::new(vec!["1", "2"]);
+        let n2 = NGram::new(vec!["1", "2"]);
+        let n3 = NGram::new(vec!["3", "4"]);
+
+        assert_eq!(n1, n2);
+        assert_ne!(n1, n3);
+        assert_ne!(n2, n3);
+    }
+
+    #[test]
+    fn test_ngram_tail() {
+        let n1 = NGram::new(vec!["1", "2", "3"]);
+        let n2 = NGram::new(vec!["2", "3"]);
+        assert_eq!(n1.tail(), n2);
+    }
+}
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diff --git a/src/util/mod.rs b/src/util/mod.rs
new file mode 100644
index 0000000..9d2ef9b
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+++ b/src/util/mod.rs
@@ -0,0 +1,130 @@
+/// Pads a sequence of words
+/// sentence: sequence to pad, in the form of an Iterator of string slices.
+/// pad_left: if set to true, prepends a padding symbol to the sentence
+/// left_pad_symbol: the padding symbol to prepend
+/// pad_right: if set to true, appends a padding symbol after the sentence
+/// right_pad_symbol: the padding symbol to append
+/// n: the n in n-grams; so for bigrams set to 2, etc
+pub fn pad_sequence<'a>(sentence: impl Iterator<Item=&'a str> + 'static, pad_left: bool, left_pad_symbol: &'static str, pad_right: bool, right_pad_symbol: &'static str, n: usize) -> impl Iterator<Item=&'a str> {
+    Padder::new(Box::new(sentence), pad_left, left_pad_symbol, pad_right, right_pad_symbol, n)
+}
+
+/// Pads a sequence of words, left-padding only. Convenience function that prevents useless arguments
+/// sentence: sequence to pad, in the form of an Iterator of string slices.
+/// left_pad_symbol: the padding symbol to prepend
+/// n: the n in n-grams; so for bigrams set to 2, etc
+pub fn pad_sequence_left<'a>(text: impl Iterator<Item=&'a str> + 'static, left_pad_symbol: &'static str, n: usize) -> impl Iterator<Item=&'a str> {
+    Padder::new(Box::new(text), true, left_pad_symbol, false, "", n)
+}
+
+/// Pads a sequence of words, right-padding only. Convenience function that prevents useless arguments
+///
+/// sentence: sequence to pad, in the form of an Iterator of string slices.
+/// pad_right: if set to true, appends a padding symbol after the sentence
+/// right_pad_symbol: the padding symbol to append
+/// n: the n in n-grams; so for bigrams set to 2, etc
+pub fn pad_sequence_right<'a>(text: impl Iterator<Item=&'a str> + 'static, right_pad_symbol: &'static str, n: usize) -> impl Iterator<Item=&'a str> {
+    Padder::new(Box::new(text), false, "", true, right_pad_symbol, n)
+}
+
+pub(crate) struct Padder<'a> {
+    n: usize,
+    text: Box<dyn Iterator<Item=&'a str>>,
+    pad_left: bool,
+    left_index: isize,
+    left_pad_symbol: &'static str,
+    pad_right: bool,
+    right_index: isize,
+    right_pad_symbol: &'static str,
+}
+
+impl<'a> Iterator for Padder<'a> {
+    type Item = &'a str;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.pad_left && self.left_index < self.n as isize {
+            self.left_index += 1;
+            return Some(self.left_pad_symbol);
+        } else {
+            let maybe_next = self.text.next();
+            if maybe_next.is_some() {
+                return maybe_next;
+            } else {
+                if self.pad_right && self.right_index < self.n as isize {
+                    self.right_index += 1;
+                    return Some(self.right_pad_symbol);
+                }
+            }
+        }
+
+        None
+    }
+}
+
+impl<'a> Padder<'a> {
+    pub(crate) fn new(text: Box<dyn Iterator<Item=&'a str>>, pad_left: bool, left_pad_symbol: &'static str,
+                      pad_right: bool, right_pad_symbol: &'static str, n: usize, ) -> Self {
+        Self { text, n, pad_left, left_index: 1, left_pad_symbol, pad_right, right_index: 1, right_pad_symbol }
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_pad_both_ends_default_n2() {
+        let text = vec!["a", "b", "c"].into_iter();
+        let padded = pad_sequence(text, true, "<s>", true, "</s>", 2);
+        assert!(equal(padded, vec!["<s>", "a", "b", "c", "</s>"].into_iter()));
+    }
+
+    #[test]
+    fn test_pad_left() {
+        let text = vec!["a", "b", "c"].into_iter();
+        let padded = pad_sequence_left(text, "<s>", 2);
+        assert!(equal(padded, vec!["<s>", "a", "b", "c"].into_iter()));
+    }
+
+    #[test]
+    fn test_pad_right() {
+        let text = vec!["a", "b", "c"].into_iter();
+        let padded = pad_sequence_right(text, "</s>", 2);
+        assert!(equal(padded, vec!["a", "b", "c", "</s>"].into_iter()));
+    }
+
+    #[test]
+    fn test_pad_both_ends_default_n_eq_3() {
+        let text = vec!["a", "b", "c"].into_iter();
+        let padded = pad_sequence(text, true, "<s>", true, "</s>", 3);
+        assert!(equal(padded, vec!["<s>", "<s>", "a", "b", "c", "</s>", "</s>"].into_iter()));
+    }
+
+    #[test]
+    fn test_pad_both_ends_non_default_symbols() {
+        let text = vec!["a", "b", "c"].into_iter();
+        let padded = pad_sequence(text, true, "left", true, "right", 2);
+        assert!(equal(padded, vec!["left", "a", "b", "c", "right"].into_iter()));
+    }
+
+    fn equal<'a>(mut l1: impl Iterator<Item=&'a str>, mut l2: impl Iterator<Item=&'a str>) -> bool {
+        loop {
+            let e1 = l1.next();
+            let e2 = l2.next();
+            if e1.is_none() {
+                return if e2.is_none() {
+                    true
+                } else {
+                    false
+                };
+            } else if e2.is_none() {
+                return false;
+            } else {
+                if e1.unwrap() != e2.unwrap() {
+                    return false;
+                }
+            }
+        }
+    }
+}
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