What is in your Mathematica tool bag? [closed]

Answer 1

PutAppend with PageWidth -> Infinity

In Mathematica using of the PutAppend command is the most straightforward way to maintain a running log file with results of intermediate computations. But it uses by default PageWith->78 setting when exporting expressions to a file and so there is no guarantee that every intermediate output will take only one line in the log.

PutAppend does not have any options itself but tracing its evaluations reveals that it is based on the OpenAppend function which has the PageWith option and allows changing its default value by the SetOptions command:

In[2]:= Trace[x>>>"log.txt",TraceInternal->True]
Out[2]= {x>>>log.txt,{OpenAppend[log.txt,CharacterEncoding->PrintableASCII],OutputStream[log.txt,15]},Null}

So we can get PutAppend to append only one line at a time by setting:

SetOptions[OpenAppend, PageWidth -> Infinity]

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UPDATE

There is a bug introduced in version 10 (fixed in version 11.3): SetOptions no longer affects the behavior of OpenWrite and OpenAppend.

A workaround is to implement your own version of PutAppend with explicit PageWidth -> Infinity option:

Clear[myPutAppend]
myPutAppend[expr_, pathtofile_String] :=
 (Write[#, expr]; Close[#];) &[OpenAppend[pathtofile, PageWidth -> Infinity]]

Note that we also may implement it via WriteString as shown in this answer, but in this case it will be necessary to preliminarily convert the expression into the corresponding InputForm via ToString[expr, InputForm].