Was sollen die Kommentar-Zeichen (%) am Ende der Zeilen?

12	In vielen Code-Beispielen und Paketen sieht man das Kommentar-Zeichen `%` am Ende von Zeilen. Wieso? Welchen Zweck erfüllen sie? leerzeichen kommentare befehle syntax gefragt 10 Jun '13, 11:51 cgnieder 22.1k●25●34●63 Akzeptiert-Rate: 60% bearbeitet 02 Dez '14, 13:57

Eine Antwort:

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Wenn TeX das Ende einer Zeile sieht, wandelt es das in ein Leerzeichen um, exakt äquivalent, als wenn man ein Leerzeichen eingegeben hätte:

Open in writeLaTeX

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Text
Text
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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ist genau gleich wie

Open in writeLaTeX

1
Text Text
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Genaugenommen wird das Zeichen eingefügt, das der Nummer des Registers \endlinechar entspricht (solange der Wert zwischen einschließlich 0 und 255 liegt). In der Voreinstellung ist das 13 und entspricht der Eingabe der Enter-Taste (carriage return, ^^M in TeX-Schreibweise mit Kategorie-Code 5=Enter-Taste). Folgt dem Ende einer Zeile ein weiteres Ende einer Zeile, wird stattdessen \par eingefügt.

In Makro-Definitionen gilt das genauso wie im laufenden Text. Die Definition

Open in writeLaTeX

Code, hier editierbar zum Übersetzen:

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\newcommand*\foo{
foo
bar
}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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ist gleich der Definition

Open in writeLaTeX

1
\newcommand*\foo{ foo bar }
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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wie folgendes Beispiel demonstriert:

Open in writeLaTeX

Code, hier editierbar zum Übersetzen:

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\documentclass{article}
\newcommand*\foo{
  foo
  bar
}
\begin{document}
bla\foo{}bar
\end{document}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Ergebnis 1

Da Leerzeichen am Anfang einer Zeile verschluckt werden, nicht aber an anderen Stellen, sollte man Leerzeichen, die durch das Ende von Zeilen verursacht werden, verstecken, damit sie nicht unbeabsichtigt an Stellen auftauchen, an denen man sie nicht möchte:

Open in writeLaTeX

Code, hier editierbar zum Übersetzen:

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\newcommand*\foo{%
  foo
  bar%
}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Diese Definition ist jetzt gleichwertig zu

Open in writeLaTeX

1
\newcommand*\foo{foo bar}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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wie dieses Beispiel demonstriert:

Open in writeLaTeX

Code, hier editierbar zum Übersetzen:

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\documentclass{article}
\newcommand*\foo{%
  foo
  bar%
}
\begin{document}
bla\foo{}bar
\end{document}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Ergebnis 2

Jetzt sollte man aber auch nicht den Schluss ziehen, dass man einfach immer an das Ende einer Zeile ein % setzen sollte. Aufpassen muss man zum Beispiel nach Zuweisungen oder Primitiven, die Zahlen nach sich erwarten, wie \ifnum oder \count\foo=.... Diese schauen nämlich so lange weiter nach Zahlen, bis sie entweder ein nichtexpandierbares Token finden, das keine Zahl ist, oder bis sie auf ein Leerzeichen finden, das sie dann entfernen. Mit folgender Definition

Open in writeLaTeX

Code, hier editierbar zum Übersetzen:

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\newcommand*\test[1]{%
  \ifnum1=#1%
    1%
  \else
    keine 1%
  \fi
}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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liefert

Open in writeLaTeX

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\test{1}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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vielleicht unerwarteterweise »keine 1«! Das liegt daran, dass die Definition gleichbedeutend ist mit

Open in writeLaTeX

1
\newcommand*\test[1]{\ifnum1=#11\else keine 1\fi}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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und tatsächlich 1 mit 11 verglichen wurde. Übrigens: nach Anweisung wie im Beispiel \else und \fi muss man kein Leerzeichen verstecken, da TeX Leerzeichen nach Anwendungen ignoriert. Eine bessere Definition des obigen wäre z.B.:

Open in writeLaTeX

Code, hier editierbar zum Übersetzen:

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\newcommand*\test[1]{%
  \ifnum1=#1 % Leerzeichen nach `#1'
    1%
  \else
    keine 1%
  \fi
}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Ähnlich vorsichtig sollte man nach Zuweisungen sein, die Skips (Längen, die dehn- und stauchbare Anteile enthalten können) zuweisen und nach plus und minus suchen.

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beantwortet 10 Jun '13, 12:21

cgnieder
22.1k●25●34●63
Akzeptiert-Rate: 60%

bearbeitet 04 Dez '14, 11:16

Eine sehr gute Übersicht darüber, wann Zeilenenden oder Leerzeichen von LaTeX als Wortzwischenraum interpretiert werden und deshalb auch in der Ausgabe landen und wann nicht, findet man übrigens in dem Artikel »Ich habe zusätzliche Leerzeichen/Einzüge in meinem Text, die da nicht hingehören. Woher kommen die?«

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beantwortet 23 Jun '13, 18:14

saputello
11.1k●17●43●65
Akzeptiert-Rate: 51%

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gestellte Frage: 10 Jun '13, 11:51

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zuletzt geändert: 04 Dez '14, 11:16

Was sollen die Kommentar-Zeichen (%) am Ende der Zeilen?

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