User guide

54 CHAPTER 3. THE LIBRARY

cptr := initco(fn, size,a,b,c,d,e,f,g,h,i,j,k) CIN:y, POS:y, NAT:y

This function provides a convenient method of creating and initialising coroutines.

It deﬁnition is as follows:

LET initco(fn, size, a, b, c, d, e, f, g, h, i, j, k) = VALOF

{ LET cptr = createco(fn, size)

result2 := 0

IF cptr DO result2 := callco(cptr, @a)

RESULTIS cptr

}

A coroutine with main funct i on fn and given size is created and, if s ucc e ssf ul , it is

initialised by callco(cptr, @a). Thus, fn should expect a vector containing up to 11

elements. Once the newly created coroutine has initialised itself, it returns control to

initco by means a call of cowait. The result of initco is the newly created coroutine

pointer , or zero on failure. The second result (in result2) is the value returned by the

ﬁrst call of cowait in the newly cr e at ed coroutine.

scb := input() CIN:y, POS:y, NAT:y

This function returns cis, the SCB of the currently selected input stream.

count := instrcount(fn,a,b,c,d,e,f,g,h,i,j,k) CIN:y, POS:y, NAT:n

This function retur ns the number of Cintco de instructions executed when eval u ati ng

the call: fn(a,b,c,d,e,f,g,h,i,j,k).

Counting starts from the ﬁrst instruction of the body of fn and ends when i ts

ﬁnal RTN instruction is executed. Thus when f was deﬁned by LET f(x) = 2*x+1,

the call instrcount(f, 10) returns 4 since its body executes the four instructions:

L2; MUL; A1; RTN. The value returned by fn(a,b,c,d,e,f,g,h,i,j,k) is saved by

instrcount in t he global variable result2.

ﬂag := intflag() CIN:y, POS:y, NAT:n

This function provides a machine dependent test to determine whether the user is

asking to interrupt t he normal execution of a program. On the Apple Macintosh ﬂag

will be set to TRUE only if the COMMAND, OPTION and SHIFT keys are simu l tane -

ously pressed.

p := level() CIN:y, POS:y, NAT:y

This call returns the current st ack frame pointer for use in a l ate r call of longjump.

segl := loadseg(name) CIN:y, POS:y, NAT:n

This function calls sys(Sys

loadseg, name) to loads the speciﬁed compiled pro-

gram into memory. Se e Sys

loadseg on page 68 for details.

longjump(P , L) CIN:y, POS:y, NAT:y

This call causes execution to resume at labe l L in the body of a function or routine

that owns the stack frame given by P that must have been obtained by a previous call of

level. Jumps may only be used to points within the current coroutine. Jumps to labels