Processing Arguments
Developing TACL Routines
3–6 107365 Tandem Computers Incorporated
The following examples illustrate two ways to retrieve a number from a position
within a line of text (as returned by FUP or other processes). First, you can use the
#CHARGET function:
#PUSH pfree line
#SET line This is a test number: 53
#SET pfree [#CHARGET line 24 FOR 2]
#OUTPUT [pfree]
The preceding code retrieves two characters from line, but does not check that the
two characters are numbers. The number at position 24 must be two characters long;
the code returns two digits even if the number has a single digit or three digits.
As an alternative, you can define a routine that uses #ARGUMENT.
?SECTION getnumber ROUTINE
#FRAME
#PUSH rslt arg position
== First, get the requested character position
#SET rslt [#ARGUMENT /TEXT position/ NUMBER OTHERWISE]
[#CASE [rslt]
|1|
== position is OK
|2|
== Caller did not supply a number for position arg.
#RESULT -1
#RETURN
]
== Skip [position] characters
SINK [#ARGUMENT CHARACTERS /WIDTH [position]/ ]
#SET rslt [#ARGUMENT /TEXT arg/ NUMBER OTHERWISE]
[#CASE [rslt]
|1|
#RESULT 0 [arg]
|2|
== Invalid argument; text at specified position is
== not a number
#RESULT -2
]
#UNFRAME
If getnumber finds a number, it returns a zero followed by the requested number. If
position is invalid, it returns -1; otherwise, it returns -2.
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