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I get the following error when I compile:

Syntax error; Undefined control sequence \EndIf

Code:

\usepackage{algorithm2e} 

\begin{algorithm}[h]
\label{FecEncodeAndSendFECUnits}
\caption{Function for Receiving and FEC-decoding FEC-encoded Units of Data}
\KwIn{}
%\KwOut{codeRate}

         nrOfPacketsReceived = 0 \
         HIGHEST\_FEC\_UNIT\_NR\_DECODED\_GLOBAL=0 \
        \While{$true$}
            currentPacket = ListenToSocketForNewPkt () \
            $ nrOfPacketsReceived++ $ \
            $ currentFecUnit =ExtractValueOfPktHeader(currentPacket, FEC_UNIT_GLOBAL) $ \
            $ currentFecUnitModulo$ = $currentFecUnit$ \% NR\_OF\_PARALLELL\_FEC\_UNITS\_GLOBAL $ \
            $ currentSymbolNr$ = ExtractValueOfPktHeader($currentPacket$, SYMBOL\_NR\_GLOBAL) $ \
              packetForCurrentFecUnitGlobal[$currentFecUnitModulo$][$currentSymbolNr$] = ExtractDataOfPkt ($currentPacket$) \
            \If { $ currentFecUnit$ > $HIGHEST_FEC_UNIT_NR_DECODED_GLOBAL$ OR
            ( currentFecUnit == 0 AND   nrOfPacketsReceived == 1 ) }
              ExtractPktHeaderAndPutIntoGlobalFecUnitHeaderValues () 
            \EndIf

             \If {currentFecUnit > HIGHEST\_FEC\_UNIT\_NR\_DECODED\_GLOBAL }            
                lastFecUnitModulo  = (currentFecUnit -1 ) \% NR\_OF\_PARALLELL\_FEC\_UNITS\_GLOBAL  \
                DecodeFECUnit (lastFecUnitModulo, nrOfSrcSymbolsGlobal[lastFecUnitModulo], nrOfTotalSymbolsGlobal[lastFecUnitModulo], symbolSizeGlobal[lastFecUnitModulo], rateOfRedundantPkts[lastFecUnitModulo]) \    
                $ HIGHEST\_FEC\_UNIT\_NR\_DECODED\_GLOBAL++$ \  
             \EndIf

        \EndWhile               

\end{algorithm}

How do I solve this?

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4  
Hi Anders, welcome to TeX.sx! :) I'm confused, I took a look at the algorithm2e documentation and found no occurrences of both \EndIf and \EndWhile. It seems the correct syntax of both \While and \If is slightly different than the one you are using. –  Paulo Cereda Aug 7 '12 at 1:09

2 Answers 2

up vote 5 down vote accepted

There's no \EndIf nor \EndWhile; you have to use parentheses to specify the scope:

\If{<condition>}{<instructions>}
\While{<condition>}{<instructions>}

So, in your case, you could use (I wasn't sure whether to insert or not line change commands \\ at some points):

\documentclass{article}
\usepackage{algorithm2e} 

\begin{document}

\begin{algorithm}[h]
\label{FecEncodeAndSendFECUnits}
\caption{Function for Receiving and FEC-decoding FEC-encoded Units of Data}
\KwIn{}
%\KwOut{codeRate}

         nrOfPacketsReceived = 0 \
         HIGHEST\_FEC\_UNIT\_NR\_DECODED\_GLOBAL=0 \\
        \While{$true$}{
            currentPacket = ListenToSocketForNewPkt () \
            $ nrOfPacketsReceived++ $ \
            $ currentFecUnit =ExtractValueOfPktHeader(currentPacket, FEC_UNIT_GLOBAL) $ \
            $ currentFecUnitModulo$ = $currentFecUnit$ \% NR\_OF\_PARALLELL\_FEC\_UNITS\_GLOBAL $ \
            $ currentSymbolNr$ = ExtractValueOfPktHeader($currentPacket$, SYMBOL\_NR\_GLOBAL) $ \
              packetForCurrentFecUnitGlobal[$currentFecUnitModulo$][$currentSymbolNr$] = ExtractDataOfPkt ($currentPacket$) \\
            \If{ $ currentFecUnit$ > $HIGHEST_FEC_UNIT_NR_DECODED_GLOBAL$ OR
            ( currentFecUnit == 0 AND   nrOfPacketsReceived == 1 ) }{
              ExtractPktHeaderAndPutIntoGlobalFecUnitHeaderValues () 
            }

             \If {currentFecUnit > HIGHEST\_FEC\_UNIT\_NR\_DECODED\_GLOBAL }{            
                lastFecUnitModulo  = (currentFecUnit -1 ) \% NR\_OF\_PARALLELL\_FEC\_UNITS\_GLOBAL  \
                DecodeFECUnit (lastFecUnitModulo, nrOfSrcSymbolsGlobal[lastFecUnitModulo], nrOfTotalSymbolsGlobal[lastFecUnitModulo], symbolSizeGlobal[lastFecUnitModulo], rateOfRedundantPkts[lastFecUnitModulo]) \    
                $ HIGHEST\_FEC\_UNIT\_NR\_DECODED\_GLOBAL++$ \  
             }
        }               
\end{algorithm}

\end{document}

enter image description here

As a side note, the algorithmicx package could be of interest for you; it has great functionality and it is highly customizable.

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Thanks for the help!! I appreciate it! –  Anders Branderud Aug 7 '12 at 16:14

You are mixing packages algorithm2e (\KwIn) with package algorithmicx. The latter uses

\If{<body>}
  <then block>
\EndIf
% also with else branches
\While{<condition>}
  <body>
\EndWhile

whereas package algorithm2e provides

\If{<condition>}{<then block>}
\While{<condition>}{<body>}

and lots of other forms.

Decide, which package you want to use and read its documentation.

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