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From mattf-horton <...@git.apache.org>
Subject [GitHub] metron pull request #606: METRON-980: Short circuit operations for Stellar
Date Wed, 07 Jun 2017 01:41:35 GMT
Github user mattf-horton commented on a diff in the pull request:

    https://github.com/apache/metron/pull/606#discussion_r119960003
  
    --- Diff: metron-platform/metron-common/src/main/java/org/apache/metron/common/stellar/StellarCompiler.java
---
    @@ -76,14 +92,80 @@ public Expression(Deque<Token<?>> tokenDeque) {
     
         public Object apply(ExpressionState state) {
           Deque<Token<?>> instanceDeque = new ArrayDeque<>();
    -      for(Iterator<Token<?>> it = getTokenDeque().descendingIterator();it.hasNext();)
{
    -        Token<?> token = it.next();
    -        if(token.getUnderlyingType() == DeferredFunction.class) {
    -          DeferredFunction func = (DeferredFunction) token.getValue();
    -          func.apply(instanceDeque, state);
    -        }
    -        else {
    -          instanceDeque.push(token);
    +      {
    +        boolean skipElse = false;
    +        Token<?> token = null;
    +        for (Iterator<Token<?>> it = getTokenDeque().descendingIterator();
it.hasNext(); ) {
    +          token = it.next();
    +          //if we've skipped an else previously, then we need to skip the deferred tokens
associated with the else.
    +          if(skipElse && token.getUnderlyingType() == ElseExpr.class) {
    +            while(it.hasNext()) {
    +              token = it.next();
    +              if(token.getUnderlyingType() == EndConditional.class) {
    +                break;
    +              }
    --- End diff --
    
    So I admit I don't fully understand the token deque, but will this work with nested if/else
statements? eg of form
    "if A1 then B1 else (if A2 then B2 else C2)"?  If A1 is true we'll want to skip all of
the level-1 else clause, not just C2.


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