Others

A call-by-value passes a copy of the value of the actuallist expression to the invoked routine by assigning the copy to a formallist variable. If the parameter is a variable, the invoked routine may change that variable.

Examples of Value:

Example 1

A call-by-reference passes a pointer to the variable of the invoked routine so operations on the assigned formallist variable also act on the actualname variable. Changes, including KILLs to the formallist variable, immediately have the same affect on the corresponding actualname variable.

Examples of Reference:

Example 1

Command postconditionals appear immediately following a command and apply to all arguments for the command when it has multiple arguments. All commands except commands that themselves have a conditional aspect accept a command postconditional. Among the M standard commands, ELSE, FOR, and IF do not accept command postconditionals. All the GT.M command extensions accept command postconditionals. When a postconditional evaluates to a literal FALSE (0), GT.M discards the command and its arguments at compile time, which means it does not perform any validity checking on the arguments.

Examples of Commands:

Example 1

C onsists of a colon (:) delimiter followed by a truth-valued expression. When the expression evaluates to true, M executes the command occurrence. When the expression evaluates to false, M does not execute the command occurrence.

Examples of Command Postconditionals:

Example 1

M provides timeouts as a tool to retain program control over commands of indefinite duration. A timeout consists of a colon (:) delimiter on an argument, followed by a numeric expression specifying the number of seconds to millisecond (three decimal place) precision for M to attempt to execute the command. When the timeout is zero (0), M makes a single attempt to complete the command.

Examples of Time out:

Example 1

Is the mechanism that controls what happens when your program encounters an error
$ETRAP contains MUMPS code to execute when an error occurs

Examples of ERROR:

Example 1

Separate parameters that the command accepts.

Examples of ,:

Example 1

Optional.

Examples of [:

Example 1

Example 2

Optional.

Examples of |:

Example 1

Example 2

Optional truth-valued expression immediately following the command is a command postconditional that controls whether or not GT.M executes the command.

Examples of tvexpr:

Example 1

Example 2

If ZHELP has no argument or expr1="", ZHELP invokes base level help; at least two (2) spaces must follow a ZHELP command with no argument to separate it from the next command on the line.

Examples of expr1:

Example 1

Example 2