ree grammar to make sure the string is well formed. The context-free grammar is described below. The scanner outputs a sequence of parser tokens. The parser tokens are almost identical to the scanner tokens, with a few exceptions; those exceptions are noted below.</P>
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The parser is passed a callback routine. The parser calls this routine when it needs information about a token; for example, if it encounters a function it does not recognize, it calls the callback to get a pointer to the function. The det