fix error

build.rs

@@ -5,12 +5,34 @@ use std::collections::HashMap;
 use std::env;
 use std::fs::File;
 use std::io::Write;
-use std::ops::{Add, Sub};
+use std::ops::{Add, Div, Mul, Sub};
 use std::path::Path;
 
 #[derive(Default, Hash, Eq, PartialEq, PartialOrd, Ord, Clone, Copy)]
 pub struct Matrix([i8; 7]);
 
+impl Mul<i8> for Matrix {
+    type Output = Matrix;
+    fn mul(self, rhs: i8) -> Self::Output {
+        let mut output = Matrix::default();
+        for (i, v) in self.0.iter().enumerate() {
+            output.0[i] = v * rhs;
+        }
+        output
+    }
+}
+
+impl Div<i8> for Matrix {
+    type Output = Matrix;
+    fn div(self, rhs: i8) -> Self::Output {
+        let mut output = Matrix::default();
+        for (i, v) in self.0.iter().enumerate() {
+            output.0[i] = v / rhs;
+        }
+        output
+    }
+}
+
 impl Add for Matrix {
     type Output = Self;
     fn add(self, rhs: Self) -> Self::Output {
@@ -223,10 +245,47 @@ fn main() {
             }
         };
         dims_mod.extend(decl);
+        let mut exponentiation = quote! {};
+        for (method_name, n) in [
+            ("square", 2),
+            ("cube", 3),
+            ("square_root", -2),
+            ("cube_root", -3),
+        ] {
+            if n == 0 {
+                continue;
+            }
+            let matrix = if n > 0 {
+                *matrix * n
+            } else {
+                if matrix.0.iter().fold(false, |a, v| a || (v % n.abs() != 0)) {
+                    continue;
+                }
+                *matrix / n.abs()
+            };
+            if let Some(derived) = dimensions.get(&matrix) {
+                let ident = format_ident!["{method_name}"];
+                let derived_ident = format_ident!["{}", derived.basename];
+                exponentiation.extend(if n > 0 {
+                    quote! {
+                        pub fn #ident(self) -> #derived_ident {
+                            #derived_ident(self.0.powf(#n.abs() as f64))
+                        }
+                    }
+                } else {
+                    quote! {
+                        pub fn #ident(self) -> #derived_ident {
+                            #derived_ident(self.0.powf(1.0 / (#n.abs() as f64)))
+                        }
+                    }
+                });
+            }
+        }
         let mut conversion = quote! {};
         conversion.extend(impl_convert(basename));
         dims_mod.extend(quote! {
             impl #basename_ident {
+                #exponentiation
                 #conversion
             }
         });
@@ -255,7 +314,16 @@ fn main() {
                 dims_mod.extend(impl_div(basename, other_basename, derived.basename));
             }
         }
-        units_mod.extend(gen_unit_structs(subunits, basename));
+        let submod_ident = format_ident!["{}", basename.to_lowercase()];
+        let unit_structs = gen_unit_structs(subunits, basename);
+        units_mod.extend(quote! {
+            pub mod #submod_ident {
+                use crate::Scale;
+                use crate::dimensions::#basename_ident;
+                #unit_structs
+            }
+            pub use #submod_ident::*;
+        });
     }
     code.extend(quote! {
         pub mod dimensions {
@@ -264,8 +332,6 @@ fn main() {
             #dims_mod
         }
         pub mod units {
-            use crate::Scale;
-            use crate::dimensions::*;
             #units_mod
         }
     });