From e97692255b863a8b47c037c5b855e00045d4dffa Mon Sep 17 00:00:00 2001
From: Andreas Longva <andreas.b.longva@gmail.com>
Date: Sun, 11 Apr 2021 08:01:30 +0200
Subject: [PATCH] Initial hacked together prototype without syn

---
 Cargo.toml                     |  2 +-
 nalgebra-macros/Cargo.toml     | 16 ++++++
 nalgebra-macros/src/lib.rs     | 99 ++++++++++++++++++++++++++++++++++
 nalgebra-macros/tests/tests.rs |  6 +++
 4 files changed, 122 insertions(+), 1 deletion(-)
 create mode 100644 nalgebra-macros/Cargo.toml
 create mode 100644 nalgebra-macros/src/lib.rs
 create mode 100644 nalgebra-macros/tests/tests.rs

diff --git a/Cargo.toml b/Cargo.toml
index 45fdb17a..ad24b809 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -92,7 +92,7 @@ matrixcompare = "0.2.0"
 itertools = "0.10"
 
 [workspace]
-members = [ "nalgebra-lapack", "nalgebra-glm", "nalgebra-sparse" ]
+members = [ "nalgebra-lapack", "nalgebra-glm", "nalgebra-sparse", "nalgebra-macros" ]
 resolver = "2"
 
 [[example]]
diff --git a/nalgebra-macros/Cargo.toml b/nalgebra-macros/Cargo.toml
new file mode 100644
index 00000000..74b5d1b2
--- /dev/null
+++ b/nalgebra-macros/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "nalgebra-macros"
+version = "0.1.0"
+authors = ["Andreas Longva <andreas.b.longva@gmail.com>"]
+edition = "2018"
+
+[lib]
+proc-macro = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+syn = "1.0"
+
+[dev-dependencies]
+nalgebra = { version = "0.25.4", path = ".." }
diff --git a/nalgebra-macros/src/lib.rs b/nalgebra-macros/src/lib.rs
new file mode 100644
index 00000000..b4e2d4b2
--- /dev/null
+++ b/nalgebra-macros/src/lib.rs
@@ -0,0 +1,99 @@
+extern crate proc_macro;
+
+use proc_macro::{TokenStream, TokenTree, Literal, Ident, Punct, Spacing, Group, Delimiter};
+use std::iter::FromIterator;
+
+struct MatrixEntries {
+    entries: Vec<Vec<TokenTree>>
+}
+
+impl MatrixEntries {
+    fn new() -> Self {
+        Self {
+            entries: Vec::new()
+        }
+    }
+
+    fn begin_new_row(&mut self) {
+        self.entries.push(Vec::new());
+    }
+
+    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())
+            .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 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!()
+    }
+}
+
+#[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)
+        }
+    }
+
+    entries.build_stream()
+}
\ No newline at end of file
diff --git a/nalgebra-macros/tests/tests.rs b/nalgebra-macros/tests/tests.rs
new file mode 100644
index 00000000..5763e139
--- /dev/null
+++ b/nalgebra-macros/tests/tests.rs
@@ -0,0 +1,6 @@
+use nalgebra_macros::matrix;
+
+#[test]
+fn basic_usage() {
+    matrix![ 1, 3; 4, 5*3];
+}
\ No newline at end of file