Merge pull request #62 from bluss/linspace

Use internal copy of linspace

Author: bluss

src/lib.rs

@@ -56,7 +56,7 @@ extern crate serde;
 #[cfg(feature = "rustc-serialize")]
 extern crate rustc_serialize as serialize;
 
-extern crate itertools as it;
+extern crate itertools;
 extern crate num as libnum;
 
 use libnum::Float;
@@ -73,7 +73,7 @@ use std::rc::Rc;
 use std::slice::{self, Iter, IterMut};
 use std::marker::PhantomData;
 
-use it::ZipSlices;
+use itertools::ZipSlices;
 
 pub use dimension::{Dimension, RemoveAxis};
 pub use dimension::NdIndex;
@@ -103,6 +103,7 @@ pub mod blas;
 mod dimension;
 mod indexes;
 mod iterators;
+mod linspace;
 mod numeric_util;
 mod si;
 mod shape_error;
@@ -544,9 +545,8 @@ impl<S> ArrayBase<S, Ix>
     pub fn linspace<F>(start: F, end: F, n: usize) -> ArrayBase<S, Ix>
         where S: Data<Elem=F>,
               F: libnum::Float,
-              usize: it::misc::ToFloat<F>,
     {
-        Self::from_iter(it::linspace(start, end, n))
+        Self::from_iter(linspace::linspace(start, end, n))
     }
 
     /// Create a one-dimensional array from interval `[start, end)`
@@ -2783,7 +2783,7 @@ pub struct Indexed<'a, A: 'a, D>(ElementsBase<'a, A, D>);
 pub struct IndexedMut<'a, A: 'a, D>(ElementsBaseMut<'a, A, D>);
 
 fn zipsl<T, U>(t: T, u: U) -> ZipSlices<T, U>
-    where T: it::misc::Slice, U: it::misc::Slice
+    where T: itertools::misc::Slice, U: itertools::misc::Slice
 {
     ZipSlices::from_slices(t, u)
 }

src/linspace.rs

@@ -0,0 +1,78 @@
+use libnum::Float;
+
+/// An iterator of a sequence of evenly spaced floats.
+///
+/// Iterator element type is `F`.
+pub struct Linspace<F> {
+    start: F,
+    step: F,
+    index: usize,
+    len: usize,
+}
+
+impl<F> Iterator for Linspace<F>
+    where F: Float,
+{
+    type Item = F;
+
+    #[inline]
+    fn next(&mut self) -> Option<F> {
+        if self.index >= self.len {
+            None
+        } else {
+            // Calculate the value just like numpy.linspace does
+            let i = self.index;
+            self.index += 1;
+            Some(self.start + self.step * F::from(i).unwrap())
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let n = self.len - self.index;
+        (n, Some(n))
+    }
+}
+
+impl<F> DoubleEndedIterator for Linspace<F>
+    where F: Float,
+{
+    #[inline]
+    fn next_back(&mut self) -> Option<F> {
+        if self.index >= self.len {
+            None
+        } else {
+            // Calculate the value just like numpy.linspace does
+            self.len -= 1;
+            let i = self.len;
+            Some(self.start + self.step * F::from(i).unwrap())
+        }
+    }
+}
+
+impl<F> ExactSizeIterator for Linspace<F> where Linspace<F>: Iterator { }
+
+/// Return an iterator of evenly spaced floats.
+///
+/// The `Linspace` has `n` elements, where the first
+/// element is `a` and the last element is `b`.
+///
+/// Iterator element type is `F`, where `F` must be
+/// either `f32` or `f64`.
+#[inline]
+pub fn linspace<F>(a: F, b: F, n: usize) -> Linspace<F>
+    where F: Float,
+{
+    let step = if n > 1 {
+        let nf: F = F::from(n).unwrap();
+        (b - a)/(nf - F::one())
+    } else {
+        F::zero()
+    };
+    Linspace {
+        start: a,
+        step: step,
+        index: 0,
+        len: n,
+    }
+}