add make_exprs.py script

scripts/make_exprs.py

@@ -0,0 +1,49 @@
+#!/usr/bin/python3.6
+
+from pathlib import Path
+
+EXPR_TYPES = {
+    'Binary': ('left: Expr', 'operator: Token', 'right: Expr'),
+    'Grouping': ('expression: Expr'),
+    'Unary': ('operator: Token', 'right: Expr'),
+
+    # NOTE: when adding new Literals, add new Literal types, instead of just
+    # doing Literal with an 'Object value'. it won't work.
+}
+
+def _gen_expr_decls():
+    res = []
+
+    for expr_type, expr_params in EXPR_TYPES.items():
+        res.append(f'pub const {expr_type} = struct {{')
+
+        for param in expr_params:
+            res.append(f'{param},')
+
+    return '\n'.join(res)
+
+
+def do_base_union(union_name: str):
+    res = [
+        'const Token = @import("token.zig").Token;\n'
+    ]
+
+    res.extend(_gen_expr_decls())
+    res.append(f'pub const {union_name} = union {{')
+
+    for expr_type in EXPR_TYPES:
+        res.append(f'{expr_type}: {expr_type},')
+
+    res.append('}\n')
+
+    return '\n'.join(res)
+
+
+def main():
+    expr_file = Path('./src') / 'expr.zig'
+    expr_file.unlink()
+    expr_file.write_text(do_base_union('Expr'))
+
+
+if __name__ == '__main__':
+    main()