Pragmatic directives: Difference between revisions

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=={{header|REXX}}==

The REXX language has ~~five~~ pragmatic statements:

The REXX language has several pragmatic statements:

::*   NUMERIC DIGITS   {nnn}

::*   NUMERIC FORM     {ENGINEERING | SCIENTIFIC}

::*   NUMERIC FORM     {ENGINEERING │ SCIENTIFIC}

::*   NUMERIC FUZZ       {nnn}

::*   OPTIONS               {xxx yyy zzz}

::*   TRACE                   {options}

::*   SIGNAL                 {ON│OFF}   SYNTAX

::*   SIGNAL                 {ON│OFF}   NOVALUE

::*   SIGNAL                 {ON│OFF}   LOSTDIGITS

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

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

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

===numeric digits===

The   '''NUMERIC DIGITS nnn'''   statement is used to specify ~~to the REXX interpreter how many~~

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

to the REXX interpreter how many

(significant) decimal digits are to be used in calculating and storing numbers.

(significant) decimal digits

are to be used in calculating and storing numbers.

'''nnn'''   can be an expression that evaluates to a ~~positive integer.~~

'''nnn'''   can be an expression that evaluates to a

positive integer.

If   '''nnn'''   is omitted, it defaults to   '''9'''.

If no   '''numeric digits'''   statement is used,   the ~~default is   '''9'''.~~

If no   '''numeric digits'''   statement is used,   the

default is   '''9'''.

It must be greater than the (current)   '''NUMERIC FUZZ'''   setting.

===numeric fuzz===

The   '''NUMERIC FUZZ nnn'''   statement is used to ~~specify to the REXX interpreter how many~~

The   '''NUMERIC FUZZ nnn'''   statement is used to

specify to the REXX interpreter how many

decimal digits   (at full precision)   will be ignored while performing arithmetic

decimal digits   (at

comparisons.

full precision)   will be ignored while performing an arithmetic

comparison.

'''nnn'''   can be an expression that evaluates to a ~~non-negative integer.~~

'''nnn'''   can be an expression that evaluates to a

non-negative integer.

If   '''nnn'''   is omitted, it defaults to   '''0'''.

If   '''nnn'''   is omitted,   it defaults to   '''0'''.

If no   '''numeric fuzz'''   statement is used,   the ~~default for REXX programs is   '''0'''.~~

If no   '''numeric fuzz'''   statement is used,   the

default for REXX programs is   '''0'''.

It must be less than the ~~(current)   '''NUMERIC DIGITS'''   setting.~~

It must be less than the

(current)   '''NUMERIC DIGITS'''   setting.

The result of using a positive value for   '''FUZZ'''   is ~~that the REXX interpreter (temporarily) reduces~~

The result of using a positive value for   '''FUZZ'''   is

that the REXX interpreter (temporarily) reduces

the number of   '''NUMERIC DIGITS'''   by the   '''FUZZ'''   value before an arithmetic comparison.

the number of   '''NUMERIC DIGITS'''   by

the   '''FUZZ'''   value before an arithmetic comparison.

This means that arithmetic comparisons are performed with the precision of

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===numeric form===

The   '''NUMERIC FORM'''   statement is used to ~~cause the REXX interpreter to use a specific form of~~

The   '''NUMERIC FORM'''   statement is used to

cause the REXX interpreter to use a specific form of

exponential format   if   the result of an arithmetic operation requires the use of exponential notation

exponential format   if   the result of an arithmetic

operation requires the use of exponential notation

with the current value of   '''numeric digits'''.

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The option can be in upper/lower/mixed case.

If no   '''numeric form'''   statement is used,   the ~~default for REXX programs is   '''scientific'''.~~

If no   '''numeric form'''   statement is used,   the

default for REXX programs is   '''scientific'''.

===options===

The   '''OPTIONS'''   statement is used to specify ~~to the REXX interpreter on such matters on how to~~

The   '''OPTIONS'''   statement is used to specify

to the REXX interpreter on such matters on how to

process the source (statements), possibly (for instance) whether or not   ''double byte character strings''

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

are present, or possibly cause the REXX interpreter to force compliance to some particular rule or

not   ''double byte character strings''  

are present, or possibly

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

REXX (program) coding standards.

There can be any number of options listed   (or none).

Each particular REXX interpreters have their ~~own   '''options''',   so it isn't considered an error if some~~

Each particular REXX interpreters have their

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

option isn't supported (or recognized) by another REXX interpreter.

Some options are global in nature, others can be enabled and disabled.

Some REXX interpreters also have a way to specify certain options via ~~the   ''command-line''  ~~

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

the   ''command-line''  

(also known as the   ''C.L.'').

===trace===

The   '''TRACE'''   statement is used to cause the REXX ~~interpreter to turn   ''off''   or ''on''   certain tracing~~

The   '''TRACE'''   statement is used to cause the REXX

interpreter to turn   ''off''   or ''on''   certain tracing

facilities for the REXX interpreter.

Most tracing options causes some sort of output   (tracing of statements ~~or values of clauses)   to be~~

Most tracing options causes some sort of output   (tracing of statements

or values of clauses)   to be

emitted to the console (terminal).

The output (tracing information) written to the terminal is usually ~~quite distinctive and can be easily~~

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

quite distinctive and can be easily

recognized.

There are a number of options for

There are numerous options for the   '''trace'''   instruction, and they won't be explained here.

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

===signal on syntax===

If the REXX interpreter detects a   syntax   error in the REXX

program,   (and the REXX interpreter

determines that the error can still be handled by the erroneous REXX

program),   control branches

to the label     '''syntax'''.   The label may be in mixed case.

===signal off syntax===

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

and terminates the

REXX program.

===signal on novalue===

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

evaluated expression,   control

branches to the label     '''novalue'''.   The label

may be in mixed case.

===signal off novalue===

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

the uppercase version

of the variable name and continue execution of the REXX program.

===signal on lostdigits===

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

results in the loss of any

decimal digits,   control branches to the

label     '''lostdigits'''.   The label may be in mixed case.

Not all REXXes support this condition (option).

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

the result of an arithmetic

operation exceeds the currently defined number

of digits via   '''numeric digits'''.

===signal off lostdigits===

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

condition and continue

execution of the REXX program.

===signal on error; call on error===

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

host system command issued by

the REXX program,   control branches to the

label     '''error'''.   The label may be in mixed case.

===signal off error; call off error===

This indicates to take the default action which means the special

variable   '''RC'''   ('''R'''eturn '''C'''ode)  

is quietly defined,   and execution continues of the REXX program.

===signal on halt; call on halt===

If the REXX interpreter detects an   external interrupt   is made to

interrupt execution of the REXX

program,   control branches to the

label     '''halt'''.   The label may be in mixed case.

The   ''external interrupt''   varies with which operating system

is being used.

===signal off halt; call off halt===

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

issued and the

execution of the REXX program is terminated.

===signal on notready; call on notready===

If the REXX interpreter detects some kind of problem with stream

I/O   (this varies with each

REXX interpreter),   control branches to the

label     '''notready'''.   The label may be in mixed case.

===signal off notready; call off notready===

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

execution of the REXX program.

Not all REXXes support this condition (option).

=={{header|Tcl}}==