BUILT-IN MATHEMATICA SYMBOL
$PreRead
$PreRead
is a global variable whose value, if set, is applied to the text or box form of every input expression before it is fed to Mathematica.
- $PreRead is always applied to each complete input string that will be fed to Mathematica.
- In multiline input with a text-based interface, whenever each line is terminated, $PreRead is typically applied to the input so far.
- $PreRead is applied to all strings returned by a $SyntaxHandler function.
- $PreRead is applied before InString[n] is assigned.
By default, $PreRead is not defined, meaning input strings are sent directly to evaluation:
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Use 
as an alias for HoldForm:
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Out[3]//FullForm= |
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Restore $PreRead to its default value:
Have Mathematica print the FullForm of parsed input expressions before evaluation:
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Restore $PreRead to its default value:
New in 2
