This is documentation for Mathematica 8, which was
based on an earlier version of the Wolfram Language.

# NHoldAll

 NHoldAllis an attribute which specifies that none of the arguments to a function should be affected by N.
• NHoldAll, NHoldFirst, and NHoldRest are useful in ensuring that arguments to functions are maintained as exact integers, rather than being converted by N to approximate numbers.
Prevent N from affecting the arguments of a function:
Prevent N from affecting the arguments of a function:
 Out[2]=
 Scope   (3)
System symbols with the NHoldAll attribute:
The arguments of Derivative remain unchanged with N:
N leaves the derivative order while changing the point of evaluation:
Define a pure function:
The function with coefficients converted to numerical values:
The positional parameters remain unchanged with N because Slot has the NHoldAll attribute:
 Applications   (2)
Use an indexed variable:
With this attribute, the variables remain unchanged:
Define a data object that represents a polynomial in a sparse form :
Make sure that N only affects the coefficients, not the powers:
Default N evaluation of the argument needs to be prevented for the rule above to work:
A representation of the polynomial :
Get the representation with approximate real coefficients:
Evaluate at :
HoldAll prevents evaluation while NHoldAll only prevents numerical evaluation:
You can prevent both by setting both attributes:
New in 3