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hkl.tex
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hkl.tex
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\subsection{Crystallographic Computations}
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The HKL object performs standard four circle calculations. I.e., given a UB
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matrix it calculates the four circle diffractometer setting angles required
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for a reflection with index hkl. The UB must be determined from a set of
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reflections found manually or automatically. This is done in an offline
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program. The code in this module is a direct reimplementation of fortran code
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provided by Jean Allibon, ILL with the MAD four circle diffractometer
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control program in ANSI-C. For theory, see the contribution by
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W.C. Hamilton in the International Tables for Crystallography, 1974 edition.
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The object uses the following object data structure:
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\begin{flushleft} \small
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\begin{minipage}{\linewidth} \label{scrap1}
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$\langle$hkldat {\footnotesize ?}$\rangle\equiv$
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\vspace{-1ex}
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\begin{list}{}{} \item
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\mbox{}\verb@@\\
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\mbox{}\verb@ typedef struct __HKL {@\\
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\mbox{}\verb@ pObjectDescriptor pDes;@\\
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\mbox{}\verb@ double fUB[9];@\\
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\mbox{}\verb@ double fLambda;@\\
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\mbox{}\verb@ int iManual;@\\
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\mbox{}\verb@ double fLastHKL[5];@\\
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\mbox{}\verb@ int iNOR;@\\
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\mbox{}\verb@ int iQuad;@\\
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\mbox{}\verb@ pMotor pTheta;@\\
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\mbox{}\verb@ pMotor pOmega;@\\
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\mbox{}\verb@ pMotor pChi;@\\
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\mbox{}\verb@ pMotor pPhi;@\\
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\mbox{}\verb@ pMotor pNu;@\\
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\mbox{}\verb@ pSelVar pMono;@\\
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\mbox{}\verb@ long lID;@\\
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\mbox{}\verb@ } HKL;@\\
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\mbox{}\verb@@$\diamond$
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\end{list}
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\vspace{-1ex}
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\footnotesize\addtolength{\baselineskip}{-1ex}
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\begin{list}{}{\setlength{\itemsep}{-\parsep}\setlength{\itemindent}{-\leftmargin}}
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\item Macro referenced in scrap ?.
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\end{list}
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\end{minipage}\\[4ex]
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\end{flushleft}
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The fields are more or less self explaining:
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\begin{description}
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\item[pDes] The standard object descriptor.
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\item[fUB] The UB matrix.
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\item[iUB] is a flag which spcifies if a UB is specified.
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\item[fLambda] The wavelength of the neutrons.
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\item[iManual] A flag which defines if the wavelength has been set manually
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or is updated automatically from a wavelength variable.
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\item[fLastHKL] the HKL of the last reflection calculated.
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\item[iNor] a flag for normal beam calculation mode.
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\item[pTheta] The two theta motor. All motor are needed for boundary
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checking.
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\item[pOmega] The omega axis motor.
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\item[pChi] The chi axis motor.
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\item[pPhi] the phi axis motor.
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\item[pNu] the nu axis motor for normal beam geometry.
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This is detector tilt.
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\item[pMono] The selector variable doing the wavelength.
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\end{description}
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The wavelength is a bit tricky. As it would be to time consuming to read two
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motors each time a calculation is performed, the lambda variable is updated
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by registering a callback with the selector variable handling the
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monochromator wavelength. As TriCS will be run with two monochromators on a
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lift a means has to be provided to change the selector variable online. An
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additonal feature is that the wavelength can be manipulated manually. This
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adresses the issue that automatic wavelength may be inaccurate due to
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lazy instrument scientists not adjusting their instruments.
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In terms of an interface the following functions will be provided by this
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module:
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\begin{flushleft} \small
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\begin{minipage}{\linewidth} \label{scrap2}
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$\langle$hklint {\footnotesize ?}$\rangle\equiv$
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\vspace{-1ex}
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\begin{list}{}{} \item
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\mbox{}\verb@@\\
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\mbox{}\verb@ typedef struct __HKL *pHKL;@\\
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\mbox{}\verb@/*-------------------------------------------------------------------------*/@\\
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\mbox{}\verb@ pHKL CreateHKL(pMotor pTheta, pMotor pOmega, @\\
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\mbox{}\verb@ pMotor pChi, pMotor pPhi, pMotor pNu);@\\
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\mbox{}\verb@ void DeleteHKL(void *pData);@\\
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\mbox{}\verb@ @\\
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\mbox{}\verb@ int HKLFactory(SConnection *pCon, SicsInterp *pSics, void *pData,@\\
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\mbox{}\verb@ int argc, char *argv[]);@\\
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\mbox{}\verb@/*------------------------------------------------------------------------*/@\\
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\mbox{}\verb@ int SetWavelengthVariable(SConnection *pCon, pHKL self, pSelVar pVar);@\\
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\mbox{}\verb@ int SetWavelengthManual(pHKL self, float fVal);@\\
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\mbox{}\verb@ int SetUB(pHKL self, float fUB[9]);@\\
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\mbox{}\verb@ int GetUB(pHKL self, float fUB[9]);@\\
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\mbox{}\verb@ int SetNOR(pHKL self, int iNOB);@\\
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\mbox{}\verb@ int GetLambda(pHKL self, float *fVal);@\\
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\mbox{}\verb@ int GetCurrentHKL(pHKL self, float fVal[3]);@\\
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\mbox{}\verb@ int GetCurrentPosition(pHKL self, SConnection *pCon, float fPosition[4]);@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@ int CalculateSettings(pHKL self, float fHKL[3], float fPsi, int iHamil,@\\
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\mbox{}\verb@ float fSet[4],SConnection *pCon);@\\
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\mbox{}\verb@ int RunHKL(pHKL self, float fHKL[3], float fPsi, int iHamil, SConnection@\\
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\mbox{}\verb@ *pCon);@\\
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\mbox{}\verb@ int DriveHKL(pHKL self, float fHKL[3], float fPsi, int iHamil,@\\
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\mbox{}\verb@ SConnection *pCon);@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@ int DriveSettings(pHKL self, float fSet[4],SConnection *pCon);@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@ int HKLAction(SConnection *pCon, SicsInterp *pSics, void *pData,@\\
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\mbox{}\verb@ int argc, char *argv[]); @\\
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\mbox{}\verb@@\\
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\mbox{}\verb@@$\diamond$
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\end{list}
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\vspace{-1ex}
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\footnotesize\addtolength{\baselineskip}{-1ex}
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\begin{list}{}{\setlength{\itemsep}{-\parsep}\setlength{\itemindent}{-\leftmargin}}
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\item Macro referenced in scrap ?.
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\end{list}
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\end{minipage}\\[4ex]
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\end{flushleft}
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All functions return 0 on failure, 1 on success if not stated otherwise.
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Most functions take a pointer to a HKL data structure as first parameter.
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The function in more detail:
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\begin{description}
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\item[CreateHKL] creates a HKL object. The parameters are pointers to the
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four four circle motors. Returns NULL on failure, a pointer to the new
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object on success.
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\item[DeleteHKL] properly removes an HKL object from the system.
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\item[HKLFactory] The factory function which initialises an HKL object from
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the initialisation script.
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\item[SetWavelengthVariable] sets a new wavelength variable. Installs all
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necesarry callbacks for automatic update.
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\item[SetWaveLengthManual] deinstall all callbacks and forces the wavelength
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to the value specified a second parameter.
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\item[SetUB] sets the UB matrix.
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\item[SetNOR] sets the normal beam calculation flag to iNOR.
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\item[CalculateSettings] is the heart of this all. As the name suggests
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calculates the settings for a four circle diffractometer. The parameters
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are:
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\begin{description}
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\item[self] A pointer to a HKL data structure.
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\item[fHKL] The reflection indices to calculate the settings for.
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\item[fPsi] The psi value for the reflection. For psi scans. Set to 0 if not
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used.
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\item[iHamil] The index of the hamilton position to calculate. Can be an
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integer between 0 to 8. 0 denotes the normal case.
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\item[fSet] contains the required settings if the function returns with
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success. 0 = two theta, 1 = omega, 2 = chi, 3 = phi.
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\end{description}
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The function returns 1 on success, a negative value on failure. Possible
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error returns are:
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\begin{description}
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\item[HKLIMPOSSIBLE] the calculation was impossible.
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\item[HKLTHETALIMIT] a setting could be calculated but can not be accessed
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due to a limit on two theta.
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\end{description}
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\item[DriveHKL] calculates a setting and drives to the position. The
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parameters are the same as with CalculateSettings. With the addition of a
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pointer to the connection object doing the command for error messages and
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everything. The error returns are the same as with CalculateSettings
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well. With the addition of HKJMOTFAIL, which means that a motor failed to
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drive properly.
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\item[DriveSettings] drives to the the settings given in fSet.
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\item[HKLAction] is the interpreter wrapper function for the HKL object.
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\end{description}
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\begin{flushleft} \small
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\begin{minipage}{\linewidth} \label{scrap3}
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\verb@"hkl.i"@ {\footnotesize ? }$\equiv$
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\vspace{-1ex}
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\begin{list}{}{} \item
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\mbox{}\verb@@\\
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\mbox{}\verb@/*-------------------------------------------------------------------------@\\
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\mbox{}\verb@ H K L@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@ Internal data structure description. See hkl.h, c,w for more details.@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@ Mark Koennecke, February 1998@\\
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\mbox{}\verb@----------------------------------------------------------------------------*/@\\
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\mbox{}\verb@@$\langle$hkldat {\footnotesize ?}$\rangle$\verb@@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@@$\diamond$
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\end{list}
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\vspace{-2ex}
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\end{minipage}\\[4ex]
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\end{flushleft}
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\begin{flushleft} \small
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\begin{minipage}{\linewidth} \label{scrap4}
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\verb@"hkl.h"@ {\footnotesize ? }$\equiv$
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\vspace{-1ex}
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\begin{list}{}{} \item
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\mbox{}\verb@@\\
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\mbox{}\verb@/*---------------------------------------------------------------------------@\\
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\mbox{}\verb@ H K L@\\
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\mbox{}\verb@ This SICS object performs angle setting calculations for a four circle @\\
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\mbox{}\verb@ diffractometer. The heart of this code is a C transcriptions of routines@\\
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\mbox{}\verb@ written by Jean Allibon at ILL for the MAD program. Theory is explained in@\\
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\mbox{}\verb@ the article by W. C. Hamilton in International Tables for Crystallography,@\\
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\mbox{}\verb@ 1974 edition.@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@ copyright: see copyright.h@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@ Mark Koennecke, February 1998@\\
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\mbox{}\verb@@\\
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\mbox{}\verb@----------------------------------------------------------------------------*/@\\
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\mbox{}\verb@#ifndef SICSHKL@\\
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\mbox{}\verb@#define SICSHKL@\\
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\mbox{}\verb@#include "selector.h"@\\
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\mbox{}\verb@#include "selvar.h"@\\
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\mbox{}\verb@@$\langle$hklint {\footnotesize ?}$\rangle$\verb@@\\
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\mbox{}\verb@#endif @\\
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\mbox{}\verb@@$\diamond$
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\end{list}
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\vspace{-2ex}
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\end{minipage}\\[4ex]
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\end{flushleft}
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