InputGen: introduce variable space (#3)

Summary:
Pull Request resolved: #3

This diff introduces the VariableSpace class.

A VariableSpace needs to be initialized with a variable type. Its purpose is to describe a space of values for that variable type. This space can be discrete (like a Python set) or it can be a union of disjoint intervals of real numbers (only for suitable variable types).

Reviewed By: digantdesai

Differential Revision: D51816908

fbshipit-source-id: e7bbfc26847bc3b1028dd15a05b441263a8497bc

Author: manuelcandales

inputgen/variable/constants.py

@@ -0,0 +1,8 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the license found in the
+# LICENSE file in the root directory of this source tree.
+
+INT64_MAX = 2**63 - 1
+INT64_MIN = -(2**63)