title: What does GNU flex library libfl provide?
body: <p>I could compile a program from flex and bison generated files by</p>
  <p><code>cc lex.yy.c program.tab.c -o output</code></p>
  <p>and also by</p>
  <p><code>cc lex.yy.c program.tab.c -lfl -o output</code></p>
  <p>They both run smoothly and without any problem.</p>
  <p>So what did <code>libfl</code> provide here? I tried to search the documentation but couldn't find a detailed explanation.</p>