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based on an earlier version of the Wolfram Language.
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$Post

$Post
is a global variable whose value, if set, is applied to every output expression.
By default, $Post is not defined, meaning output comes directly from evaluation:
Set $Post to N so that all expressions are evaluated numerically after evaluation:
Restore $Post to the default:
Set $Post to Simplify so that symbolic simplification is tried on each output:
Restore $Post to the default:
By default, $Post is not defined, meaning output comes directly from evaluation:
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Out[1]=
 
Set $Post to N so that all expressions are evaluated numerically after evaluation:
In[1]:=
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In[2]:=
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Out[2]=
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Out[3]=
Restore $Post to the default:
In[4]:=
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Set $Post to Simplify so that symbolic simplification is tried on each output:
In[1]:=
Click for copyable input
In[2]:=
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Out[2]=
In[3]:=
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Out[3]=
Restore $Post to the default:
In[4]:=
Click for copyable input
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