Initial impl using syn and quote

nalgebra-macros/Cargo.toml

@@ -10,7 +10,10 @@ proc-macro = true
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-syn = "1.0"
+# TODO: Determine minimal features that we need
+syn = { version="1.0", features = ["full"] }
+quote = "1.0"
+proc-macro2 = "1.0"
 
 [dev-dependencies]
 nalgebra = { version = "0.25.4", path = ".." }

nalgebra-macros/src/lib.rs

@@ -1,99 +1,85 @@
 extern crate proc_macro;
 
-use proc_macro::{TokenStream, TokenTree, Literal, Ident, Punct, Spacing, Group, Delimiter};
-use std::iter::FromIterator;
+use syn::{Expr};
+use syn::parse::{Parse, ParseStream, Result, Error};
+use syn::punctuated::{Punctuated};
+use syn::{parse_macro_input, Token};
+use quote::{quote, format_ident};
+use proc_macro::TokenStream;
 
-struct MatrixEntries {
-    entries: Vec<Vec<TokenTree>>
+struct Matrix {
+    // Represent the matrix as a row-major vector of vectors of expressions
+    rows: Vec<Vec<Expr>>,
+    ncols: usize,
 }
 
-impl MatrixEntries {
-    fn new() -> Self {
-        Self {
-            entries: Vec::new()
+impl Matrix {
+    fn nrows(&self) -> usize {
+        self.rows.len()
+    }
+
+    fn ncols(&self) -> usize {
+        self.ncols
+    }
+
+    fn to_col_major_repr(&self) -> Vec<Expr> {
+        let mut data = Vec::with_capacity(self.nrows() * self.ncols());
+        for j in 0 .. self.ncols() {
+            for i in 0 .. self.nrows() {
+                data.push(self.rows[i][j].clone());
+            }
         }
+        data
     }
+}
 
-    fn begin_new_row(&mut self) {
-        self.entries.push(Vec::new());
-    }
+type MatrixRowSyntax = Punctuated<Expr, Token![,]>;
+type MatrixSyntax = Punctuated<MatrixRowSyntax, Token![;]>;
 
-    fn push_entry(&mut self, entry: TokenTree) {
-        if self.entries.is_empty() {
-            self.entries.push(Vec::new());
-        }
-        let mut last_row = self.entries.last_mut().unwrap();
-        last_row.push(entry);
-    }
-
-    fn build_stream(&self) -> TokenStream {
-        let num_rows = self.entries.len();
-        let num_cols = self.entries.first()
-            .map(|first_row| first_row.len())
+impl Parse for Matrix {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let span = input.span();
+        // TODO: Handle empty matrix case
+        let ast = MatrixSyntax::parse_separated_nonempty_with(input,
+            |input| MatrixRowSyntax::parse_separated_nonempty(input))?;
+        let ncols = ast.first().map(|row| row.len())
             .unwrap_or(0);
 
-        // First check that dimensions are consistent
-        for (i, row) in self.entries.iter().enumerate() {
-            if row.len() != num_cols {
-                panic!("Unexpected number of columns in row {}: {}. Expected {}", i, row.len(), num_cols);
+        let mut rows = Vec::new();
+
+        for row in ast {
+            if row.len() != ncols {
+                // TODO: Is this the correct span?
+                // Currently it returns the span corresponding to the first element in the macro
+                // invocation, but it would be nice if it returned the span of the first element
+                // in the first row that has an unexpected number of columns
+                return Err(Error::new(span, "Unexpected number of columns. TODO"))
             }
+            rows.push(row.into_iter().collect());
         }
 
-        let mut array_tokens = Vec::new();
-
-        // Collect entries in column major order
-        for i in 0 .. num_rows {
-            for j in 0 .. num_cols {
-                let entry = &self.entries[i][j];
-                array_tokens.push(entry.clone());
-                array_tokens.push(TokenTree::Punct(Punct::new(',', Spacing::Alone)));
-            }
-        }
-
-        let row_dim = format!("U{}", num_rows);
-        let col_dim = format!("U{}", num_cols);
-        // let imports = format!("use nalgebra::\{Matrix, {}, {}\};", row_dim, col_dim);
-        // let constructor = format!("Matrix::<_, {}, {}>::from_slice", row_dim, col_dim);
-        // let array_group = Group::new(Delimiter::Bracket, TokenStream::from_iter(array_tokens.into_iter()));
-
-        let array_stream = TokenStream::from_iter(array_tokens);
-
-        // TODO: Build this up without parsing?
-        format!(r"{{
-            nalgebra::MatrixMN::<_, nalgebra::{row_dim}, nalgebra::{col_dim}>::from_column_slice(&[
-                {array_tokens}
-            ])
-        }}", row_dim=row_dim, col_dim=col_dim, array_tokens=array_stream.to_string()).parse().unwrap()
-
-
-        // let mut outer_group = Group::new(Delimiter::Brace,
-        //
-        // );
-
-
-        // TODO: Outer group
-
-
-
-
-        // todo!()
+        Ok(Self {
+            rows,
+            ncols
+        })
     }
 }
 
 #[proc_macro]
 pub fn matrix(stream: TokenStream) -> TokenStream {
-    let mut entries = MatrixEntries::new();
-    for tree in stream {
-        match tree {
-            // TokenTree::Ident(ident) => entries.push_entry(tree),
-            // TokenTree::Literal(literal) => entries.push_entry(tree),
-            TokenTree::Punct(punct) if punct == ';' => entries.begin_new_row(),
-            TokenTree::Punct(punct) if punct == ',' => {},
-            // TokenTree::Punct(punct) => panic!("Unexpected punctuation: '{}'", punct),
-            // TokenTree::Group(_) => panic!("Unexpected token group"),
-            _ => entries.push_entry(tree)
-        }
-    }
+    let matrix = parse_macro_input!(stream as Matrix);
 
-    entries.build_stream()
+    let dim_ident = |dim| format_ident!("U{}", dim);
+    let row_dim = dim_ident(matrix.nrows());
+    let col_dim = dim_ident(matrix.ncols());
+    let entries_col_major = matrix.to_col_major_repr();
+
+    //  TODO: Use quote_spanned instead??
+    // TODO: Construct directly from array?
+    let output = quote! {
+        nalgebra::MatrixMN::<_, nalgebra::dimension::#row_dim, nalgebra::dimension::#col_dim>
+            ::from_column_slice(&[#(#entries_col_major),*])
+    };
+
+    proc_macro::TokenStream::from(output)
 }

nalgebra-macros/tests/tests.rs

@@ -2,5 +2,7 @@ use nalgebra_macros::matrix;
 
 #[test]
 fn basic_usage() {
-    matrix![ 1, 3; 4, 5*3];
+    matrix![ 1, 3;
+             4, 5*3;
+             3, 3];
 }