Support min_tokens in sgl.gen (#1573)

examples/frontend_language/usage/sgl_gen_min_tokens.py

@@ -0,0 +1,35 @@
+"""
+This example demonstrates how to use `min_tokens` to enforce sgl.gen to generate a longer sequence
+
+Usage:
+python3 sgl_gen_min_tokens.py
+"""
+
+import sglang as sgl
+
+
+@sgl.function
+def long_answer(s):
+    s += sgl.user("What is the capital of the United States?")
+    s += sgl.assistant(sgl.gen("answer", min_tokens=64, max_tokens=128))
+
+
+@sgl.function
+def short_answer(s):
+    s += sgl.user("What is the capital of the United States?")
+    s += sgl.assistant(sgl.gen("answer"))
+
+
+if __name__ == "__main__":
+    runtime = sgl.Runtime(model_path="meta-llama/Meta-Llama-3.1-8B-Instruct")
+    sgl.set_default_backend(runtime)
+
+    state = long_answer.run()
+    print("=" * 20)
+    print("Longer Answer", state["answer"])
+
+    state = short_answer.run()
+    print("=" * 20)
+    print("Short Answer", state["answer"])
+
+    runtime.shutdown()