S3 (programming language)

Annotated Example

 MODE KMT_BUFFER IS BYTE;
 MODE KMT_STRING IS REFBYTE;
 MODE KMT_WORD IS REFBYTE;
 
 MODE KMT_MTM_VALUES IS ANY
 BYTE RVB_VALUE,
 REFREFBYTE RVRVB_VALUE);
 
 MODE KMT_PP_PACKET_STATISTICS_S IS STRUCT
 ;

 EXT PROC KMT_UI;
 
 EXT PROC KMT_PH;
 
 EXT PROC KMT_PP_GET_PACKET,
 PROC KMT_PP_SEND_PACKET,
 PROC KMT_PP_BUILD_STRING_PACKET_DATA;

 EXT REF BYTE KMT_VERSION;
 
 EXT REF BOOL ASG_ROUTE;
 
 EXT REFKMT_MTM_VALUES KMT_MTM_AREA;
 EXT REFBYTE MTM_TEXT;
 EXT REF INT MTM_TEXT_LEN;
 EXT REF REF BYTE MTM_RECALL_DATA;

 GLOBAL STATIC PROC KERMIT_THE_FROG IS
 REFBYTE OPTION,
 REFBYTE VME_FILE,
 REFBYTE REM_FILE,
 :
 
 BEGIN
 
 BYTE JSV_NAME := "ASG"; @ obtain value for ASG_ROUTE bool @
 CTM_JS_READ;
 IF RC_IGNORED NE 0 THEN ASG_ROUTE := FALSE FI;
 
 @ verify parameter references : @
 @ OPTION must be of mode REF BYTE, may not be ZLR or NIL @
 @ VME_FILE must be of mode REF BYTE, may be ZLR, must not be NIL @
 @ REM_FILE must be of mode REF BYTE, may be ZLR, must not be NIL @
 
 UNLESS 
 AND 
 AND 
 THEN  @ invalid parameter reference @
 RESULT := 10002 @ ARCH_INACCESSIBLE_PARAMETER @
 
 ELSF  @ create resource block @
 CTM_JS_BEGIN;
 RESULT <= 0
 THEN  @ resource block created @
 LONG LONG WORD KERMIT_RESULT;
 ANYLONG WORD AS_LW, PARAMS;
 PARAMS.AS_LW := ;
 
  @ set up program error handler @
 IF KMT_EH_INFORM_PE_CONTINGENCY;
 RESULT > 0
 THEN  @ failed to set error handler @
 SKIP
 ELSF CTM_JS_CALL; @ create firewall @
 RESULT <= 0
 THEN @ either exited normally or via CTM_STOP @
 RESULT := IF <= 0
 THEN 0  @ ignore warnings @
 ELSE 52000 @ error return common resultcode @
 FI
 FI;
 
 CTM_JS_END @ end resource block @
 FI
 
 END

• The declaration of the procedure is decorated with annotations that define a command line syntax allowing the program to be called from SCL, or used from an interactive shell with prompting for default parameter values.
• Procedure calls prefixed CTM are calls to the "Compiler Target Machine", an API offered by the VME operating system.
• "JSV" means "job space variable", VME's term for an environment variable, and the call on CTM_JS_READ reads the value of the variable.
• UNLESS means "if not"; ELSF means "else if".
• LONG LONG WORD declares a 128-bit integer, which is a native type supported by the 2900 architecture
• The bulk of the processing is delegated to another procedure, KERMIT_SUPPORT, which can be found in the same module. This is called indirectly via the operating system CTM_JS_CALL, similar to an exec call on Unix systems; this ensures clean failure handling and tidying up of any resources in the event of a fatal error. The PDESC keyword constructs a "procedure descriptor": essentially it treats KERMIT_SUPPORT as a first-class function which can be passed as an argument to another function, making CTM_JS_CALL a higher-order function that calls its supplied argument with appropriate error handling.