Start a Modula-2 experiment

README.md

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+# Elna programming language
+
+Elna is a simple, imperative, low-level programming language.
+
+It is intendet to accompany other languages in the areas, where a high-level
+language doesn't fit well. It is also supposed to be an intermediate
+representation for a such high-level hypothetical programming language.
+
+## File extension
+
+.elna
+
+## Current implementation
+
+This repository contains a GCC frontend for Elna. After finishing the frontend
+I'm planning to rewrite the compiler in Elna itself with its own backend and
+a hand-written parser. So GCC gives a way to have a simple bootstrap compiler
+and a possbility to compile Elna programs for different platforms.
+
+## Grammar
+
+program = block "." ;
+
+block = [ "const" ident "=" number {"," ident "=" number} ";"]
+        [ "var" ident {"," ident} ";"]
+        { "procedure" ident ";" block ";" } statement ;
+
+statement = [ ident ":=" expression | "call" ident 
+              | "?" ident | "!" expression 
+              | "begin" statement {";" statement } "end" 
+              | "if" condition "then" statement 
+              | "while" condition "do" statement ];
+
+condition = "odd" expression |
+            expression ("="|"#"|"<"|"<="|">"|">=") expression ;
+
+expression = [ "+"|"-"] term { ("+"|"-") term};
+
+term = factor {("*"|"/") factor};
+
+factor = ident | number | "(" expression ")";
+
+## Build
+
+The frontend requires GCC 14.2.0 (not tested with other versions).
+
+Download the GCC source. Copy the contents of this repository into `gcc/elna`
+inside GCC. Finally build GCC enabling the frontend with
+`--enable-languages=c,c++,elna`. After the installation the compiler can be
+invoked with `$prefix/bin/gelna`.
+
+There is also a `Rakefile` that downloads, builds and installs GCC into the
+`./build/` subdirectory. The `Rakefile` assumes that ruby and rake, as well as
+all GCC dependencies are already available in the system. It works under Linux
+and Mac OS. In the latter case GCC is patched with the patches used by Homebrew
+(official GCC doesn't support Apple silicon targets). Invoke with
+
+```sh
+rake boot
+```
+
+See `rake -T` for more tasks. The GCC source is under `build/tools`. The
+installation path is `build/host/install`.