Convert (n-1) to F instead subtracting F::one()

This makes the implementation clearer and avoids the issue that
`One::one()` is defined to be the multiplicative identity, not
necessarily `F::from(1)`.

Author: jturner314

src/geomspace.rs

@@ -85,8 +85,8 @@ where
     let log_a = a.abs().ln();
     let log_b = b.abs().ln();
     let step = if n > 1 {
-        let nf: F = F::from(n).unwrap();
-        (log_b - log_a) / (nf - F::one())
+        let num_steps = F::from(n - 1).expect("Converting number of steps to `A` must not fail.");
+        (log_b - log_a) / num_steps
     } else {
         F::zero()
     };

src/linspace.rs

@@ -73,8 +73,8 @@ 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())
+        let num_steps = F::from(n - 1).expect("Converting number of steps to `A` must not fail.");
+        (b - a) / num_steps
     } else {
         F::zero()
     };

src/logspace.rs

@@ -78,8 +78,8 @@ where
     F: Float,
 {
     let step = if n > 1 {
-        let nf: F = F::from(n).unwrap();
-        (b - a) / (nf - F::one())
+        let num_steps = F::from(n - 1).expect("Converting number of steps to `A` must not fail.");
+        (b - a) / num_steps
     } else {
         F::zero()
     };