Update dataframe.rs

charming/src/datatype/dataframe.rs

@@ -109,3 +109,39 @@ macro_rules! vec_len {
     };
 }
 
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_macro_input, Ident, LitStr};
+
+#[proc_macro]
+pub fn transpose(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as syn::ExprTuple);
+
+    let vectors: Vec<_> = input.elems.iter().map(|expr| {
+        match expr {
+            syn::Expr::Lit(syn::ExprLit { lit: syn::Lit::Str(s), .. }) => {
+                let ident = Ident::new(&s.value(), s.span());
+                quote! { #ident }
+            }
+            _ => panic!("Expected vector identifiers"),
+        }
+    }).collect();
+
+    let len = vectors.len();
+    let first_vec = &vectors[0];
+
+    let expanded = quote! {
+        {
+            let mut result = Vec::with_capacity(#len);
+            for i in 0..#first_vec.len() {
+                result.push(vec![
+                    #((#vectors[j])[i]),*
+                ]);
+            }
+            result
+        }
+    };
+
+    expanded.into()
+}
+