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Chapter 7.
Suspended
Function Execution
SUSPENSION
The execution
of
a user-defined function can
be
interrupted (suspended)
in
a var-
iety
of
ways: by an
error
message (see Chapter 11),
by
pressing ATTN (see
Chapter 1),
or
by using
the
stop
control vector
(see
Chapter 6).
In
any case,
the
suspended function
is
still considered active, since its
execution
can be resumed.
Whatever
the
reason
for
the
suspension, when it occurs,
the
statement
number
of
the
next
statement
to
be executed
is
displayed. A branch
to
the
statement
num-
ber
that
was displayed
or
a branch
to
0
LC
(~D
LC,
see Chapter 5) causes normal
continuation
of
the
function,
and a branch
out
(-+0)
exits
the
function.
When a function
is
suspended,
the
5100
will:
• Contintle
to
execute system commands
except
)SAVE, )COPY, and )PCOPY.
• Resume execution
of
the
function
at
statement
n when
~n
is
entered.
• Reopen
the
definition
of
any function
that
is
not
pendent.
A
pendent
func-
tion
is
a function
that
called
the
suspended
function.
If
a function called a
function
that
called a suspended function (and
so
on),
it
is
also
pendent
(see
State Indicator
in
this chapter).
• Execute other- functions or expressions.
Note: The display
of
output
generated by previous
statements
might have been
interrupted J.then
the
suspension occurred. This would
be
caused by
the
delay
between execution
of
the
statement
and
the
display
of
the
output.
STATE
INDICA~OR
The state indicator identifies which functions are suspended (*)
and
at
what
point
normal execution can be resumed. Entering
)SI
causes a display
of
the
state indi-
cator. Such a display might have
the
following form:
HI:7J
G[2]
F[~3]
This display indicates
that
execution was halted just before
statement
7
of
func-
tion
H,
that
the
current
use
of
function H was invoked in
statement
2
of
function
G, and
that
the
use
of
function G was invoked in
statement
3
of
F.
The
*
appearing
to
the
right of H[7] indicates
that
function H
is
suspended;
the
func-
tions G and F are said
to
be
pendent.
155
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