From 67cdcc2e12118becb823e20a40cc2687f2b8425a Mon Sep 17 00:00:00 2001
From: Adam Carpenter <53hornet@gmail.com>
Date: Wed, 27 Mar 2019 15:32:37 -0400
Subject: Started Rust in Action MEAP.

---
 meap/meap-code/ch5/ch5-u8-to-mock-rand.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 meap/meap-code/ch5/ch5-u8-to-mock-rand.rs

(limited to 'meap/meap-code/ch5/ch5-u8-to-mock-rand.rs')

diff --git a/meap/meap-code/ch5/ch5-u8-to-mock-rand.rs b/meap/meap-code/ch5/ch5-u8-to-mock-rand.rs
new file mode 100644
index 0000000..46ac91a
--- /dev/null
+++ b/meap/meap-code/ch5/ch5-u8-to-mock-rand.rs
@@ -0,0 +1,17 @@
+// fn mock_rand(n: u8) -> f32 {
+//     (n as f32) / 255.
+// }
+
+fn mock_rand(n: u8) -> f32 {
+    let base: u32 = 0b0_01111110_00000000000000000000000; // <1> Underscores mark the sign/mantissa/exponent boundaries
+    let large_n =  (n as u32) << 15; // <2> Align the input byte `n` to 32 bits, then increase its value  by shifting its bits 15 places to the left 
+    let f32_bits = base | large_n; // <3> Take a bitwise OR, merging the base with the input byte
+    let m = f32::from_bits(f32_bits);// <4> Interpret `f32_bits` (which is type `u32`) as an `f32`
+    2.0 * ( m - 0.5 ) // <5> Normalize the output range
+}
+
+fn main() {
+    println!("max of input range: {:08b} -> {}", 0xff, mock_rand(0xff));
+    println!("mid of input range: {:08b} -> {}", 0x77, mock_rand(0x77));
+    println!("min of input range: {:08b} -> {}", 0x00, mock_rand(0x00));    
+}
\ No newline at end of file
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