# NAG CL Interfacee04whc (nlp2_​option_​double_​set)

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## 1Purpose

e04whc may be used to supply individual double optional parameters to e04wdc. The initialization function e04wcc must have been called before calling e04whc.

## 2Specification

 #include
 void e04whc (const char *string, double rvalue, Nag_E04State *state, NagError *fail)
The function may be called by the names: e04whc, nag_opt_nlp2_option_double_set or nag_opt_nlp_option_set_double.

## 3Description

e04whc may be used to supply values for double optional parameters to e04wdc. It is only necessary to call e04whc for those arguments whose values are to be different from their default values. One call to e04whc sets one argument value.
Each double optional parameter is defined by a single character string in string and the corresponding value in rvalue. For example the following illustrates how the $LU$ stability tolerance could be defined:
```factol = 100.0;
if (illcon) factol = 5.0;
e04whc ("LU Factor Tolerance", factol, &state, &fail);```
Optional parameter settings are preserved following a call to e04wdc and so the keyword ${\mathbf{Defaults}}$ is provided to allow you to reset all the optional parameters to their default values before a subsequent call to e04wdc.
A complete list of optional parameters, their abbreviations, synonyms and default values is given in Section 12 in e04wdc.

None.

## 5Arguments

1: $\mathbf{string}$const char * Input
On entry: a single valid keyword of a double optional parameter (as described in Section 12 in e04wdc).
2: $\mathbf{rvalue}$double Input
On entry: the value associated with the keyword in string.
3: $\mathbf{state}$Nag_E04State * Communication Structure
state contains internal information required for functions in this suite. It must not be modified in any way.
4: $\mathbf{fail}$NagError * Input/Output
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

## 6Error Indicators and Warnings

NE_ALLOC_FAIL
Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
On entry, argument $⟨\mathit{\text{value}}⟩$ had an illegal value.
NE_E04_OPTION_INVALID
The supplied option is invalid. Check that the keywords are neither ambiguous nor misspelt. The option string is ‘$⟨\mathit{\text{value}}⟩$’ and ${\mathbf{rvalue}}=⟨\mathit{\text{value}}⟩$.
NE_E04WCC_NOT_INIT
The initialization function e04wcc has not been called.
NE_INTERNAL_ERROR
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 7.5 in the Introduction to the NAG Library CL Interface for further information.
NE_NO_LICENCE
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.

Not applicable.