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Numeric constants are either integer or floating point real numbers, as illustrated in the following example: 

int iValue;
real rValue;    
iValue = 1234;      // assigns integer to constant
iValue = 0777;      // assigns integer to constant octal 777 (decimal 511)
ivalue = 0xff;      // assigns integer to constant hex ff (decimal 255)
rValue = 32.1;      // assigns real to a constant
rValue = 3.21e1;    // real constant in exponential notation

Note that numeric constants can only be used in context with the implied constant type. The implied type of a constant is integer unless there is a decimal place or the constant is in exponential format. You can use a type cast to change the type of a constant if required (see Casting Types). 

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StringConstants StringConstants

String Constants

String(16) sName;
Strcpy_STR(sName,"Bill");   // copies the constant "Bill" to string variable sName

Special characters in a string can be defined using escape sequences.  An escape sequence consists of a backslash character (\) followed by one or more characters.  The following table defines the ANSI escape sequences supported in GXC: 

If a backslash character precedes a character not specified in the table, The undefined character is interpreted as the character itself. If a backslash appears as the last character in a line (immediately before a new line character), the next line is considered a continuation of the current line. This can be useful for defining long string constants. 

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DefiningConstants DefiningConstants

Defining Constants

#define TWOPI  6.2831853
rCirc = TWOPI * rRadius;  // seen as rCirc = 6.2831853 * rRadius

#define iDUMMY -2147483647
#define rDUMMY -1.0E32

Note that #define statement lines cannot contain comments.

You can use the backslash character before the end of a line to define a long string constant that continues onto the next line: 

#define LONG_STR “Long"Long strings can be br\<para xmlns="http://ddue.schemas.microsoft.com/authoring/2003/5" />
okenbroken into two or more \
pieces.”"

Note that if there are any white-space characters following the backslash, other than a newline character, the continuation is not recognised. 

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Functions Functions

Function Identifiers

GXs call functions to perform most of the real processing work and to control the Oasis montaj interface. The suite of functions available to the GX programmer is called the GX API, or GX Application Programming Interface. Before calling a function, the function identifier must be declared in a function prototype statement. All Geosoft function prototypes are defined in the GXH files in the GxDev/gxh directory. You can refer to GX Function Libraries for more information on working with GX functions in the GX API.

A function prototype statement is normally contained in a separate GXH file that is included (using the #include directive) in your source code immediately before your variable declarations. Following is the syntax for a function identifier: 

[dll_name] return_type function_name(arg_1_type,arg_2_type,…);  

For example, the following prototype defined the function identifier ReadReal_BF in the BF class, which can be used to read a real value from a binary file: 

[_public] void   
ReadReal_BF(BF,    // BF handle
            int,   // BF element type, one of GS_? types in <legacyBold xmlns="http://ddue.schemas.microsoft.com/authoring/2003/5">Geosoft.gxh</legacyBold>Geosoft.gxh
            var real); // real data returned