Pragmatic directives: Difference between revisions

The REXX language has several pragmatic statements:

::*   NUMERIC DIGITS   {nnn}

::*   NUMERIC FORM     {ENGINEERING │ SCIENTIFIC}

::*   NUMERIC FUZZ       {nnn}

::*   OPTIONS               {xxx yyy zzz}

::*   TRACE                   {options}

::*   SIGNAL                 {ON│OFF}   LOSTDIGITS

::*   SIGNAL                 {ON│OFF}   NOVALUE

::*   SIGNAL                 {ON│OFF}   SYNTAX

::*   SIGNAL│CALL       {ON│OFF}   ERROR

::*   SIGNAL│CALL       {ON│OFF}   FAILURE

::*   SIGNAL│CALL       {ON│OFF}   HALT

::*   SIGNAL│CALL       {ON│OFF}   NOTREADY

The   '''NUMERIC DIGITS nnn'''   statement is used to specify

to the REXX interpreter how many

<br>(significant) decimal digits

are to be used in calculating and storing numbers.

'''nnn''' &nbsp; can be an expression that evaluates to a

positive integer.

If no &nbsp; '''numeric digits''' &nbsp; statement is used, &nbsp; the

default is &nbsp; '''9'''.

The &nbsp; '''NUMERIC FUZZ nnn''' &nbsp; statement is used to

specify to the REXX interpreter how many

<br>decimal digits &nbsp; (at

full precision) &nbsp; will be ignored while performing an arithmetic

<br>comparison.

'''nnn''' &nbsp; can be an expression that evaluates to a

non-negative integer.

If no &nbsp; '''numeric fuzz''' &nbsp; statement is used, &nbsp; the

default for REXX programs is &nbsp; '''0'''.

It must be less than the

(current) &nbsp; '''NUMERIC DIGITS''' &nbsp; setting.

The result of using a positive value for &nbsp; '''FUZZ''' &nbsp; is

that the REXX interpreter (temporarily) reduces

<br>the number of &nbsp; '''NUMERIC DIGITS''' &nbsp; by

the &nbsp; '''FUZZ''' &nbsp; value before an arithmetic comparison.

The &nbsp; '''NUMERIC FORM''' &nbsp; statement is used to

cause the REXX interpreter to use a specific form of

<br>exponential format &nbsp; if &nbsp; the result of an arithmetic

operation requires the use of exponential notation

If no &nbsp; '''numeric form''' &nbsp; statement is used, &nbsp; the

default for REXX programs is &nbsp; '''scientific'''.

The &nbsp; '''OPTIONS''' &nbsp; statement is used to specify

to the REXX interpreter on such matters on how to

<br>process the source (statements), possibly (for instance) whether or

not &nbsp; ''double byte character strings'' &nbsp;

<br>are present, or possibly

cause the REXX interpreter to force compliance to some particular rule or

Each particular REXX interpreters have their

own &nbsp; '''options''', &nbsp; so it isn't considered an error if some

Some REXX interpreters also have a way to specify certain options via

the &nbsp; ''command-line'' &nbsp;

The &nbsp; '''TRACE''' &nbsp; statement is used to cause the REXX

interpreter to turn &nbsp; ''off'' &nbsp; or ''on'' &nbsp; certain tracing

Most tracing options causes some sort of output &nbsp; (tracing of statements

or values of clauses) &nbsp; to be

The output (tracing information) written to the terminal is usually

quite distinctive and can be easily

There are a number of options for

the &nbsp; '''trace''' &nbsp; instruction, and they won't be explained here.

If the REXX interpreter detects that a result of any arithmetic operation

results in the loss of any

<br>decimal digits, &nbsp; control branches to the

label &nbsp; &nbsp; '''lostdigits'''. &nbsp; The label may be in mixed case.

This condition is raised when the number of significant decimal digits in

the result of an arithmetic

<br>operation that would exceed the currently defined number

of digits via &nbsp; '''numeric digits'''.

This indicates to take the default action which is quietly ignore the

condition and continue

If the REXX interpreter detects an uninitialized variable is used in an

evaluated expression, &nbsp; control

<br>branches to the label &nbsp; &nbsp; '''novalue'''. &nbsp; The label

may be in mixed case.

This indicates to take the default action which is to quietly return the value of

the uppercase version

If the REXX interpreter detects a &nbsp; syntax &nbsp; error in the REXX

program, &nbsp; (and the REXX interpreter

<br>determines that the error can still be handled by the erroneous REXX

program), &nbsp; control branches

This indicates to take the default action which REXX issues an error message

and terminates the

If the REXX interpreter detects a &nbsp; non-zero &nbsp; return code from a

host system command issued by

<br>the REXX program, &nbsp; control branches to the

label &nbsp; &nbsp; '''error'''. &nbsp; The label may be in mixed case.

This indicates to take the default action which means the special

variable &nbsp; '''RC''' &nbsp; ('''R'''eturn '''C'''ode) &nbsp;

If the REXX interpreter detects a &nbsp; failure &nbsp; from a

host system command issued by the REXX

<br>program, &nbsp; control branches to the

label &nbsp; &nbsp; '''failure'''. &nbsp; The label may be in mixed case.

This indicates to take the default action which means the special

variable &nbsp; '''RC''' &nbsp; ('''R'''eturn '''C'''ode) &nbsp;

If the REXX interpreter detects an &nbsp; external interrupt &nbsp; is made to

interrupt execution of the REXX

<br>program, &nbsp; control branches to the

label &nbsp; &nbsp; '''halt'''. &nbsp; The label may be in mixed case.

<br>The &nbsp; ''external interrupt'' &nbsp; varies with which operating system

is being used.

This indicates to take the default action which normally means a message is

issued and the

If the REXX interpreter detects some kind of problem with stream

I/O &nbsp; (this varies with each

<br>REXX interpreter), &nbsp; control branches to the

label &nbsp; &nbsp; '''notready'''. &nbsp; The label may be in mixed case.

This indicates to take the default action which is to quietly resume

execution of the REXX program.

The scope for the all the above statements &nbsp; (except for '''options'''), &nbsp; if

issued in the main program,

If the above statements are issued in an internal routine, upon return from

that routine, &nbsp; the

<br>original status is restore &nbsp; (to just before the

invoke of that routine).