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Mathematica > Core Language > Expressions > Evaluation Control >

Built-in Mathematica Symbol

NHoldFirst

NHoldFirst
is an attribute which specifies that the first argument to a function should not be affected by N.

Prevent N from affecting the first argument of a function:

System symbols with the NHoldFirst attribute:

The

zero of the zeta function on the critical line with the imaginary part greater than

N does not affect the index

When the second argument is numeric, N evaluates numerically:

Define an "inverse" for

Set the NHoldFirst attribute so that

remains an integer:

A symbolic representation of an inverse of

This remains unmodified with N:

With a numeric value of x, the function binv evaluates numerically:

HoldFirst prevents evaluation while NHoldFirst only prevents numerical evaluation:

You can prevent both by setting both attributes: