[base] change struct name Sign to Signum (as it includes zero).

Signum is the mathematical function defined on real numbers which
takes the values -1,0,+1.

This should help to distinguish this struct from logically different
uses, such as negation of expressions in the parser.

Author: youngman-g

base/src/onescomplement.rs

@@ -6,10 +6,11 @@ pub mod error;
 pub(crate) mod signed;
 pub(crate) mod unsigned;
 
-/// The sign of a number.  Although in a one's-complement system all
-/// values have a sign, we treat zero specially in order to simplify
-/// working with native types and one's-complement types together.
-pub(crate) enum Sign {
+/// The sign of a number (mathematically, sgn(x)).  Although in a
+/// one's-complement system all values have a sign, we treat zero
+/// specially in order to simplify working with native types and
+/// one's-complement types together.
+pub(crate) enum Signum {
     Negative = -1, // <= -1
     Zero = 0,      // +0 or -0
     Positive = 1,  // >= +1
@@ -19,5 +20,5 @@ pub(crate) enum Sign {
 /// [`signed`] module) and unsigned types (defined in the [`unsigned`]
 /// module).
 pub(crate) trait WordCommon {
-    fn signum(&self) -> Sign;
+    fn signum(&self) -> Signum;
 }

base/src/onescomplement/signed.rs

@@ -4,7 +4,7 @@ use std::hash::{Hash, Hasher};
 
 use super::error::ConversionFailed;
 use super::unsigned::*;
-use super::{Sign, WordCommon};
+use super::{Signum, WordCommon};
 
 #[cfg(test)]
 mod tests18;
@@ -318,13 +318,13 @@ macro_rules! signed_ones_complement_impl {
         }
 
         impl WordCommon for $SelfT {
-            fn signum(&self) -> Sign {
+            fn signum(&self) -> Signum {
                 if self.is_zero() {
-                    Sign::Zero
+                    Signum::Zero
                 } else if self.is_negative() {
-                    Sign::Negative
+                    Signum::Negative
                 } else {
-                    Sign::Positive
+                    Signum::Positive
                 }
             }
         }

base/src/onescomplement/unsigned.rs

@@ -14,7 +14,7 @@ use serde::Serialize;
 use super::super::subword::{right_half, split_halfword, split_halves};
 use super::error::ConversionFailed;
 use super::signed::*;
-use super::{Sign, WordCommon};
+use super::{Signum, WordCommon};
 
 #[cfg(test)]
 mod tests;
@@ -257,13 +257,13 @@ macro_rules! unsigned_ones_complement_impl {
         }
 
         impl WordCommon for $SelfT {
-            fn signum(&self) -> Sign {
+            fn signum(&self) -> Signum {
                 if self.is_zero() {
-                    Sign::Zero
+                    Signum::Zero
                 } else if self.is_negative() {
-                    Sign::Negative
+                    Signum::Negative
                 } else {
-                    Sign::Positive
+                    Signum::Positive
                 }
             }
         }

base/src/types.rs

@@ -9,7 +9,7 @@ use std::hash::{Hash, Hasher};
 use super::onescomplement::error::ConversionFailed;
 use super::onescomplement::signed::{Signed18Bit, Signed5Bit, Signed6Bit};
 use super::onescomplement::unsigned::{Unsigned18Bit, Unsigned36Bit, Unsigned6Bit};
-use super::onescomplement::{Sign, WordCommon};
+use super::onescomplement::{Signum, WordCommon};
 
 /// The `IndexBy` trait implements address arithmetic (adding a signed
 /// or unsigned value to an address).
@@ -181,9 +181,9 @@ fn signed_idx_impl(base: Address, delta: Signed18Bit) -> Result<Address, Convers
     let (current, mark) = base.split();
     let abs_delta: Unsigned18Bit = Unsigned18Bit::try_from(i32::from(delta.abs()))?;
     let physical = match delta.signum() {
-        Sign::Zero => current,
-        Sign::Positive => current.wrapping_add(abs_delta),
-        Sign::Negative => current.wrapping_sub(abs_delta),
+        Signum::Zero => current,
+        Signum::Positive => current.wrapping_add(abs_delta),
+        Signum::Negative => current.wrapping_sub(abs_delta),
     } & !PLACEHOLDER_MARK_BIT;
     Ok(Address::join(physical, mark))
 }