Open Watcom FORTRAN 77 Language Reference

Language Reference
9.12 GUESS-ADMIT-END GUESS
GUESS [: block-label]
statement(s)
ADMIT
statement(s)
ADMIT
statement(s)
.
.
.
ADMIT
statement(s)
END GUESS
The GUESS-ADMIT-END GUESS structure is a rejection mechanism which is useful when sets of
statements are to be conditionally chosen for execution, but not all of the conditions required to make a
selection are available beforehand. It is an extension to FORTRAN 77. The sets of statements to be chosen
may be thought of as alternatives, the first alternative being statements immediately after the GUESS
statement. Execution begins with the statements in the first alternative. If a condition is detected which
indicates that the first alternative was the wrong choice, a QUIT statement may be executed to cause
control to be passed to the statements after the ADMIT statement (i.e., the second alternative). A QUIT
statement within the second alternative passes control to the third alternative, etc. A QUIT statement
within the last alternative passes control to the statement after the END GUESS statement. If an alternative
completes execution without encountering a QUIT statement (i.e., all statements are executed up to the next
ADMIT statement) then control is passed to the statement after the END GUESS statement. An optional
block label may be specified following the keyword GUESS (see the QUIT statement for more
information).
In the following example, two sets of codes and numbers are read in and some simple sequence checking is
performed. If a sequence error is detected an error message is printed and processing terminates; otherwise
the numbers are processed and another pair of numbers is read.
206 GUESS-ADMIT-END GUESS