diff options
| author | Camil Staps | 2016-04-28 08:06:02 +0200 |
|---|---|---|
| committer | Camil Staps | 2016-04-28 14:45:09 +0200 |
| commit | b807028edf7f1f5122dbf53d6a44e2d327b87a0c (patch) | |
| tree | c924eb958882f18053e7c86a9724be8676742aae /rulesexec.tex | |
| parent | Fixes (diff) | |
Unescape
Diffstat (limited to 'rulesexec.tex')
| -rw-r--r-- | rulesexec.tex | 34 |
1 files changed, 29 insertions, 5 deletions
diff --git a/rulesexec.tex b/rulesexec.tex index 127fe7e..3c70599 100644 --- a/rulesexec.tex +++ b/rulesexec.tex @@ -38,7 +38,7 @@ $$ \begin{cases} \lambda & \text{als $s=\lambda$}\\ \parsepgm{s'} & \text{als $s=c~s'$ met $c$ whitespace}\\ - \parsestr{s'} & \text{als $s=\texttt{\char`\"}~s'$} \\ + \parsestr{s'} & \text{als $s=\texttt{"}~s'$} \\ \StmCat:\parsepgm{s'} & \text{als $s=\texttt{+}~s'$} \\ \StmHead:\parsepgm{s'} & \text{als $s=\texttt{h}~s'$} \\ \StmTail:\parsepgm{s'} & \text{als $s=\texttt{t}~s'$} \\ @@ -58,14 +58,38 @@ Dit is in overeenkomst met de specificatie, maar op zich niet nodig. $$ \parsestr s = \begin{cases} - \lambda:\parsepgm{s'} & \text{als $s=\texttt{\char`\"}~s'$} \\ - \texttt{\textbackslash}~k~\parsestr{s'} & \text{als $s=\texttt{\textbackslash}~k~s'$ met - $k \in\Char$} \\ + \lambda:\parsepgm{s'} & \text{als $s=\texttt{"}~s'$} \\ + \unescape{c}~\parsestr{s'} & \text{als $s=\texttt{\textbackslash}~c~s'$ + met $c \in\Char$} \\ c~\parsestr{s'} & \text{als $s=c~s'$ met $c - \in\Char\setminus\{\texttt{\char`\",\textbackslash}\}$}\\ + \in\Char\setminus\{\texttt{"},\texttt{\textbackslash}\}$}\\ \end{cases} $$ Het tweede geval van $\parsestrop$ zorgt ervoor dat ge-escapete aanhalingstekens de string niet beëindigen. +Hierbij gebruiken we $\unescapeop$ om bepaalde karakters te unescapen: + +$$ + \unescape c = + \begin{cases} + \text{het LF-karakter} & \text{als $c=\texttt{n}$} \\ + \texttt{"} & \text{als $c=\texttt{"}$} \\ + \texttt{\textbackslash} & \text{als $c=\texttt{\textbackslash}$} \\ + \texttt{\textbackslash~$c$} & \text{anderszins} + \end{cases} +$$ + +Het laatste alternatief geeft aan dat `ongeldige escape sequences' worden +behandeld alsof de backslash er twee keer stond. Dit is in overeenstemming met +het commentaar op de specificatie en met de Perl interpreter: %todo referentie +\begin{quote} + This [the specification] does not specify the behaviour of invalid escape + sequences. The Perl interpreter treats invalid escape sequences as if the + backslash had occured twice - that is, \textbackslash X is treated as + \textbackslash\textbackslash X. For maximum compatibility, Smurf programs + should not rely on this behaviour and should always ensure valid escape + sequences are used. +\end{quote} + |