# Synopsis

PDX_MSGT gdx_EvalCompositeDerivs(long option, T_GDX_COMP_CURVE *gdx_composite, int max_deriv, double tval, double (*derivs)[3])

# Purpose

Evaluate derivatives on a GDX composite curve

# Description

Given the GDX composite curve definition and a parameter value, evaluates the requested derivatives in a GDX composite curve. The tval parameter is the unnormalized composite curve parameter value by default. A max_deriv > 3 returns 0.0 derivative values.

# Input

## option

### GDX_UNNORM

Unnormalize the parameter value

### GDX_FROMLEFT

Evaluate derivatives from the left. Derivatives are evaluated from the right by default.

## gdx_composite

The GDX composite curve data structure

## tval

The parameter value to evaluate

## max_deriv

The maximium derivative required

# Output

## derivs

Resulting 3D derivatives

# Return

          GDX_NOERR
          Low level error return
          .fi