feat: basic impl of a u64 with const 9 decimals

.github/workflows/actions/rust-toolchain/action.yml

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+name: rust-toolchain
+inputs:
+  toolchain:
+    description: "Which rust toolchain to use"
+    required: false
+
+runs:
+  using: "composite"
+  steps:
+    - id: get-toolchain
+      shell: bash
+      run: |
+        USER_OVERRIDE=${{ inputs.toolchain }}
+        DEFAULT_TOOLCHAIN=$(grep channel rust-toolchain.toml | awk '{print $3}' | sed 's/"//g')
+        TOOLCHAIN=${USER_OVERRIDE:-$DEFAULT_TOOLCHAIN}
+        echo "toolchain=$TOOLCHAIN" >> $GITHUB_OUTPUT
+
+    - uses: actions-rs/toolchain@v1
+      with:
+        profile: minimal
+        toolchain: ${{ steps.get-toolchain.outputs.toolchain }}
+        override: true
+    - uses: Swatinem/rust-cache@v2.0.0
+      with:
+        shared-key: ${{ steps.get-toolchain.outputs.toolchain }}

.github/workflows/ci.yml

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+name: ci-rust-push
+
+on:
+  push:
+    branches:
+      - 'main'
+      - 'master'
+
+jobs:
+  skip-duplicates:
+    runs-on: ubuntu-latest
+    outputs:
+      should_skip: ${{ steps.skip_check.outputs.should_skip }}
+    steps:
+      - id: skip_check
+        uses: fkirc/skip-duplicate-actions@v5
+        with:
+          concurrent_skipping: "same_content_newer"
+
+  check:
+    needs: skip-duplicates
+    if: needs.skip-duplicates.outputs.should_skip != 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+      - uses: ./.github/workflows/actions/rust-toolchain
+      - run: cargo check --all-features
+
+  test:
+    needs: skip-duplicates
+    if: needs.skip-duplicates.outputs.should_skip != 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+      - uses: ./.github/workflows/actions/rust-toolchain
+      - run: cargo test --all-features
+
+  fmt:
+    needs: skip-duplicates
+    if: needs.skip-duplicates.outputs.should_skip != 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+      - uses: ./.github/workflows/actions/rust-toolchain
+        with:
+          toolchain: nightly
+      - run: rustup component add rustfmt
+      - run: cargo fmt --all --check
+
+  clippy:
+    needs: skip-duplicates
+    if: needs.skip-duplicates.outputs.should_skip != 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+      - uses: ./.github/workflows/actions/rust-toolchain
+      - run: rustup component add clippy
+      - run: cargo clippy --all-features -- --deny warnings
+
+  doc:
+    needs: skip-duplicates
+    if: needs.skip-duplicates.outputs.should_skip != 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+      - uses: ./.github/workflows/actions/rust-toolchain
+      - run: cargo doc --all-features --no-deps

.gitignore

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+/target
+/logs

Cargo.toml

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+[package]
+name = "const-decimal"
+version = "0.1.0"
+authors = ["Oliver Chalk"]
+edition = "2021"
+readme = "README.md"
+
+[lints.clippy]
+cast_possible_truncation = 'warn'
+cast_possible_wrap = 'warn'
+cast_sign_loss = 'warn'
+# See `clippy.toml`.
+disallowed_methods = 'warn'
+
+[features]
+serde = ["dep:serde"]
+
+[dependencies]
+serde = { version = "1.0.210", features = ["derive"], optional = true }
+
+[build-dependencies]
+
+[profile.release]
+opt-level = 3
+debug = true
+
+[profile.paranoid]
+inherits = "release"
+overflow-checks = true
+debug-assertions = true
+
+[profile.performance]
+inherits = "release"
+lto = "fat"
+codegen-units = 1
+incremental = false

README.md

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+# Const Point
+
+Fixed precision maths type implemented using compile time constants.

clippy.toml

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+[[disallowed-methods]]
+path = "core::cmp::Ord::min"
+reason = '''
+Too easy to misread `x.min(y)` as "let the minimum value of `x` be `y`" when it actually means the exact opposite;
+Use `std::cmp::min` instead.
+'''
+
+[[disallowed-methods]]
+path = "core::cmp::Ord::max"
+reason = '''
+Too easy to misread `x.max(y)` as "let the maximum value of `x` be `y`" when it actually means the exact opposite;
+Use `std::cmp::max` instead.
+'''

rust-toolchain.toml

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+[toolchain]
+channel = "1.76.0"

rustfmt.toml

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+edition = "2021"
+error_on_line_overflow = true
+wrap_comments = true
+use_field_init_shorthand = true
+imports_granularity = "Module"
+condense_wildcard_suffixes = true
+format_strings = true
+group_imports = "StdExternalCrate"
+use_small_heuristics = "Max"
+chain_width = 60

src/lib.rs

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+use std::ops::{Add, Div, Mul, Sub};
+
+pub const PRECISION_FACTOR: u64 = 10u64.pow(9);
+
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Decimal64(pub u64);
+
+impl Decimal64 {
+    pub const ONE: Decimal64 = Decimal64(PRECISION_FACTOR);
+}
+
+impl Add for Decimal64 {
+    type Output = Self;
+
+    #[inline]
+    fn add(self, rhs: Self) -> Self::Output {
+        Decimal64(self.0 + rhs.0)
+    }
+}
+
+impl Sub for Decimal64 {
+    type Output = Self;
+
+    #[inline]
+    fn sub(self, rhs: Self) -> Self::Output {
+        Decimal64(self.0 - rhs.0)
+    }
+}
+
+impl Mul for Decimal64 {
+    type Output = Self;
+
+    #[inline]
+    fn mul(self, rhs: Self) -> Self::Output {
+        Decimal64(self.0 * rhs.0 / PRECISION_FACTOR)
+    }
+}
+
+impl Div for Decimal64 {
+    type Output = Self;
+
+    #[inline]
+    fn div(self, rhs: Self) -> Self::Output {
+        Decimal64(self.0 * PRECISION_FACTOR / rhs.0)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn add() {
+        assert_eq!(Decimal64::ONE + Decimal64::ONE, Decimal64(PRECISION_FACTOR * 2));
+    }
+
+    #[test]
+    fn sub() {
+        assert_eq!(Decimal64::ONE - Decimal64::ONE, Decimal64(0));
+    }
+
+    #[test]
+    fn mul() {
+        assert_eq!(Decimal64::ONE * Decimal64::ONE, Decimal64::ONE);
+    }
+
+    #[test]
+    fn div() {
+        assert_eq!(Decimal64::ONE / Decimal64::ONE, Decimal64::ONE);
+    }
+}

taplo.toml

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+[formatting]
+column_width = 120
+array_auto_expand = true
+allowed_blank_lines = 1
+
+[[rule]]
+keys = ["dependencies", "dev-dependencies", "build-dependencies", "toolchain", "workspace.dependencies"]
+
+[rule.formatting]
+reorder_keys = true