Started work on the grammar generator.

src/generate_grammar.py

+#!/usr/bin/python
+argmap ={'REG': 'WORD'}
+
+def command(name, args):
+    """Generate grammar code to be pasted in grammar.y for a sinle MIPS
+    command."""
+    argc = len(args)
+    mapped_args = [argmap[arg] if arg in argmap else arg for arg in args]
+    code = '"%s" %s {\n' % (name, ' COMMA '.join(mapped_args))
+    code += '\t\tchar **argv = (char **)malloc(%d * sizeof(char *));\n' % argc
+    code += '\t\tint *argt = (int *)malloc(%d * sizeof(int));\n' % argc
+
+    for i, argtype in enumerate(args):
+        code += '\t\targv[%d] = $%d;\n' % (i, i * 2 + 2)
+        code += '\t\targt[%d] = ARG_%s;\n' % (i, argtype)
+
+    code += '\t\tadd_line(TYPE_CMD, %s, %d, argv, argt);\n' % (name, argc)
+    code += '\t}\n'
+
+    return code
+
+# Define commands
+commands = [ \
+            (['add', 'sub'], ['REG'] * 3), \
+            (['addi', 'subi'], ['REG', 'REG', 'INT']), \
+        ]
+
+# Generate 'command' grammar
+cmd = []
+
+for names, args in commands:
+    for name in names:
+        cmd.append(command(name, args))
+
+code = 'commands:\n\t%s\t;\n' % '\t| '.join(cmd)
+
+print code