DCL:MATH1:Summary:FORTRAN77 Standard
The GLpGET/GLpSET of the SYSLIB, the
"bulletin board of parameters" of DCL, is a library that has used to
the fullest extent the previously introduced technique of hiding parameters
that do not have to be specified each time. The GLpGET/GLpSET
only hands over parameters to other programs, and does nothing else. It has the
following structure (it is simplified from the actual source).
(Note: In the DCL ver. 5, it is possible to intervene on internal variables using runtime parameters, so internally, the GLpGET/GLpSET calls a subroutine. The following explanation uses the of the DCL ver. 4. The structure of the subroutines for ver. 5 is basically the same as the GLpGET/GLpSET of ver. 4.)
*----------------------------------------------- * GLPGET / GLPSET *----------------------------------------------- SUBROUTINE GLPGET(CP,IPARA) CHARACTER CP*(*) PARAMETER (NPARA=17) INTEGER IX(NPARA) REAL RX(NPARA) LOGICAL LX(NPARA) CHARACTER CPARA(NPARA)*8 EQUIVALENCE (IX,RX,LX) SAVE DATA CPARA( 1)/'NBITSPW '/, IX( 1)/32/ ........ DATA CPARA(12)/'LMISS '/, LX(12)/.FALSE./ DATA CPARA(13)/'IMISS '/, IX(13)/999/ DATA CPARA(14)/'RMISS '/, RX(14)/999.0/ ........ DO 10 N=1,NPARA IF (CP.EQ.CPARA(N)) THEN IPARA=IX(N) RETURN END IF 10 CONTINUE Error handling STOP *----------------------------------------------- ENTRY GLPSET(CP,IPARA) DO 15 N=1,NPARA IF (CP.EQ.CPARA(N)) THEN IX(N)=IPARA RETURN END IF 15 CONTINUE Error handling STOP END
Here, a parameter name is registered to the character variable CPARA,
and values corresponding to the parameter name are assigned to the variables IX, RX, LX
. (These 3 variables are coupled by the EQUIVALENCE statement, so they actually
occupy only a single memory area.)
The function IMAX of IFALIB is used to find the maximum value excluding the missing value. IMAX acquires the integer value representing the missing value from the argument, and in turn, executes the statement
CALL GLPGET('IMISS', IMISS)
Then, the GLPGET searches for the name 'IMISS' from CPARA
(lines 24-29), and returns the value corresponding to the name as the IMISS
value. The returned value is specified by the DATA statement, but when
necessary, this value can be changed in advance by GLISET.
The reason why this method is better compared to the method introduced in the
previous Section 1.5.3 (where each program has its own
ENTRY statement for setting IMISS ) is because the information held by
GLPGET can be inquired from multiple subroutines. For example, the
initial value of all missing values is given as 999, but in the case where 999
falls within the range of possible data, this value must be changed. With this
method, the GLPSET only has to be called once to control the operation
of all subroutines that handles missing values.