Using Caché ObjectScript - InterSystems Documentation

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User-defined Code Similarly, a reference to a tag within indirection or an Xecute is to a tag outside of the procedure. Hence Goto @A is not supported within a procedure, since a Goto from within a procedure must be to a tag within the procedure. Other parts of the documentation contain more detail on indirection and the Xecute command. Similarly, when you issue a Job command within a procedure, it starts a child process that is outside the method. This means that for code such as the following: Kill ^MyVar Job MyLabel Quit $$$OK MyLabel Set ^MyVar=1 Quit In order for the child process to be able to see the label, the method or the class cannot be contained in a procedure block. 8.2.8 Error Traps within Procedures If an error trap gets set from within a procedure, it needs to be directly to a private tag in the procedure. (This is unlike in legacy code, where it can contain “+offset” or a routine name. This rule is consistent with the idea that executing an error trap essentially means unwinding the stack back to the error trap and then executing a Goto.) If an error occurs inside a procedure, $ZERROR gets set to the procedure “ tag+offset”, not to a private “tag+offset”. To set an error trap, the normal $ZTRAP or $ETRAP is used, but the value must be a literal. For instance: Set $ZT = "abc" // sets the error trap to the private tag "abc" within this block For more information on error traps, see the chapter of this document on Error Processing. 8.3 Legacy User-Defined Code Before the addition of procedures to Caché, there was support for user-defined code in the form of subroutines and functions (which themselves can now be implemented as procedures). These legacy entities are described here, primarily to help explicate already-written code; their ongoing use is not recommended. 8.3.1 Subroutines 8.3.1.1 Syntax Routine syntax: label [ ( param [ = default ][ , ...] ) ] /* code */ Quit Invoking syntax: Do label [ ( param [ , ...] ) ] or Goto label 86 Using Caché ObjectScript
Legacy User-Defined Code label param default code The name of the subroutine. A standard label. It must start in column one. The parameter parentheses following the label are optional. If specified, the subroutine cannot be invoked using a Goto call. Parameter parentheses prevent code execution from “falling through” into a subroutine from the execution of the code that immediately precedes it. When Caché encounters a label with parameter parentheses (even if they are empty) it performs an implicit Quit, ending execution rather than “falling through.” The parameter value(s) passed from the calling program to the subroutine. A subroutine invoked using the Goto command cannot have param values, and must not have parameter parentheses. A subroutine invoked using the Do command may or may not have param values. If there are no param values, empty parameter parentheses may be specified or omitted. Specify a param variable for each parameter expected by the subroutine. The expected parameters are known as the formal parameter list.. There may be none, one, or more than one param. Multiple param values are separated by commas. Caché automatically invokes New on the referenced param variables. Parameters may be passed to the formal parameter list by value or by reference. An optional default value for the param preceding it.You can either provide or omit a default value for each parameter. A default value is applied when no actual parameter is provided for that formal parameter, or when an actual parameter is passed by reference and the local variable in question does not have a value. This default value must be a literal: either a number, or a string enclosed in quotation marks. You can specify a null string (“ ”) as a default value. This differs from specifying no default value, because a null string defines the variable, whereas the variable for a parameter with no specified or default value would remain undefined. If you specify a default value that is not a literal, Caché issues a error. A block of code. This block of code is normally accessed by invoking the label. However, it can also be entered (or reentered) by calling another label within the code block or issuing a label + offset Goto command. A block of code can contain nested calls to other subroutines, functions, or procedures. It is recommended that such nested calls be performed using Do commands or function calls, rather than a linked series of Goto commands. This block of code is normally exited by an explicit Quit command; this Quit command is not always required, but is a recommended coding practice.You can also exit a subroutine by using a Goto to an external label. 8.3.1.2 Description A subroutine is a block of code identified by a label found in the first column position of the first line of the subroutine. Execution of a subroutine most commonly completes by encountering an explicit Quit statement. A subroutine is invoked by either the Do command or the Goto command. • A Do command executes a subroutine and then resumes execution of the calling routine. Thus, when Caché encounters a Quit command in the subroutine, it returns to the calling routine to execute the next line following the Do command. • A Goto command executes a subroutine but does not return control to the calling program. When Caché encounters a Quit command in the subroutine, execution ceases. You can pass parameters to a subroutine invoked by the Do command; you cannot pass parameters to a subroutine invoked by the Goto command. You can pass parameters by value or by reference. See Parameter Passing. The same variables are available to a subroutine and its calling routine. A subroutine does not return a value. Using Caché ObjectScript 87
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Using Caché ObjectScript Version 2
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Table of Contents About This Book .
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5.7.3 Specifying a Combination Patt
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10.2 Manipulating Multidimensional
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15.6.2 Database Conversion ........
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List of Tables Table 3-1: Date Form
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1 Introducing Caché ObjectScript C
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Invoking Commands and Functions 1.3
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2 Syntax Rules This chapter describ
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Comments • White space must appea
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Literals 2.5 Literals A literal is
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Labels These prefix characters iden
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3 Data Types and Values Caché Obje
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Numbers 3.2.1 Fundamentals of Numbe
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Objects You can use the $DOUBLE fun
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Dates 3.7 Dates Caché ObjectScript
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Variables reserved for system use a
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Variables 4.1.2.2 Listing Process-p
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Variables Other examples of special
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Variables 4.3 Variable Declaration
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Operators and Expressions ObjectScr
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Operators and Expressions For those
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Traditional Error Processing If a s
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Traditional Error Processing • Ha
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Traditional Error Processing to an
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Traditional Error Processing Passin
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Traditional Error Processing 1. Cac
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14 Command-line Routine Debugging T
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Debugging with the Caché Debugger
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Debugging With BREAK If you had not
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Debugging With BREAK use the line e
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Debugging With BREAK %SYS>BREAK "L"
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Using %STACK to Display the Stack L
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Using %STACK to Display the Stack F
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Other Debugging Tools 14.4 Other De
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Other Debugging Tools Note: %ER is
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Open M Language Compatibility WRITE
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Open M Language Compatibility • Y
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Open M Language Compatibility Param
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Open M Language Compatibility Bit 2
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Open M Language Compatibility • $
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Open M Language Compatibility • I
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Open M Language Compatibility The C
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Open M Language Compatibility • Z
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Open M Language Compatibility Cach
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