meta data for this page
  •  

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revisionBoth sides next revision
choice_points [2020/10/02 08:32] – revuskychoice_points [2020/10/08 12:17] – revusky
Line 104: Line 104:
 Now, to be clear, looking ahead one token might be sufficient or not in any given spot, but if we don't specify any extra information, that is the //default assumption//. Another fancy, theoretical way of expressing this //default// would be: Now, to be clear, looking ahead one token might be sufficient or not in any given spot, but if we don't specify any extra information, that is the //default assumption//. Another fancy, theoretical way of expressing this //default// would be:
  
-//We enter an expansion at a choice point if the next token is in that expansion's **first set**.//+//We enter an expansion at a choice point if the next token is in that expansion's [[first set]].//
  
-Again, no need to be intimidated by the lingo. An expansion's //first set// is simply the set of tokens with which an expansion can begin. Depending how your brain is wired, it might be easier to think about it the other way round. Like so:+Again, no need to be intimidated by the lingo. An expansion's [[first set]] is simply the set of tokens with which an expansion can begin. Depending how your brain is wired, it might be easier to think about it the other way round. Like so:
  
-//If the next token is **not** in an expansion's **first set**, the expansion cannot possibly be matched, so we skip ahead to the following choice.//+//If the next token is **not** in an expansion's [[first set]], the expansion cannot possibly be matched, so we skip ahead to the following choice.//
  
 Now, regardless, it may be the case that more than one of the expansions at a given choice point matches this condition. Well, in that case, we have a secondary rule: //the first one gets it//. And this is really no different, by the way, from how if-elseif-else in a procedural programming language works. Now, regardless, it may be the case that more than one of the expansions at a given choice point matches this condition. Well, in that case, we have a secondary rule: //the first one gets it//. And this is really no different, by the way, from how if-elseif-else in a procedural programming language works.