*** COSC3308 SNOBOL EXAMPLE PROGRAM-5 11/22/2004

*** File: RecPatt.sno

*** 1. Fullscan/Quickscan (Default: &Fullscan=0)

*** Fullscan makes recursive pattern fail sometimes

*** especially when a recursive definition is given as the

*** first alternate.

*** 2. UnEvaluated Expression (The unary *) given as a part

*** of pattern structure is not evaluated until actual pattern

*** matching takes place thereby postponing its evaluation, which may

*** not always work in QuickScan mode.

*** 3. QuickScan assumes that *E (Unevaluation exp) matches at least

*** one character

*** 4. In QuickScan, "ARB" behaves the same in unanchored mode as in

*** anchored mode.

1 &Fullscan = 0

2 FT1 = *FT1 "A" | "A" ;* Recursion first alternate as first-component

3 Ft2 = 'A' *Ft2 | 'A' ;* Recursion first alternate as second-component

4 SD1 = "A" | *SD1 "A" ;* Recursion second alternate as first-component

5 Sd2 = 'A' | 'A' *Sd2 ;* Recursion second alternate as second-component

6 string = "AAAA"

7 OUTPUT = "RECURSION SECOND ALTERNATE as first component, QUICKSCAN"

8 string SD1 $ OUTPUT FAIL

9 Output = "Recursion SECOND ALTERNATE as second component, QUICKSCAN"

10 string SD2 $ Output Fail

11 OUTPUT = "RECURSION FIRST ALTERNATE as first component, QUICKSCAN"

12 string FT1 $ OUTPUT FAIL

13 output = "recursion FIRST ALTERNATE as second component, QuickScan"

14 string Ft2 $ Output Fail

15 output =

16 OUTPUT =

17 OUTPUT = "NOW FULLSCAN MODE:::::"

18 Output =

19 &FullScan = 1

20 OUTPUT = "RECURSION SECOND ALTERNATE as Second component"

21 string Sd2 $ Output Fail ;* Same outputs as "QuickScan" with no stack overflow.

22 output = "Recursion SECOND ALTERNATE as First component"

23 string SD1 $ OUTPUT FAIL ;* Stack overflow error after all matching

* substrings are printed out only starting with position-1

* although Unanchored.

24 OUTPUT = "RECURSION FIRST ALTERNATE as second component:"

* string FT2 $ FAIL ;*Stack overflow even before the first output

25 define('PRINT(X,Y,Z)')

26 define('PP()')

27 THREE = LEN(1) $ A ARB LEN(1) $ B ARB LEN(1) $ C

27 + *PRINT(A,B,C) FAIL

28 OUTPUT = "ALL COMBINATIONS IN FULLSCAN:"

29 "12345" THREE

30 OUTPUT = "NOW QUICKSCAN MODE: ONLY FIRST TWO"

31 &FullScan = 0

32 "12345" THREE :(End)

33 PP Loop = Loop + 1

34 OUTPUT = "REPEATING COUNT::" Loop :(RETURN)

35 Print OUTPUT = X ' ' Y ' ' Z " " :(RETURN)

36 END

RECURSION SECOND ALTERNATE as first component, QUICKSCAN

A

AA

AAA

AAAA

A

AA

AAA

A

AA

A

Recursion SECOND ALTERNATE as second component, QUICKSCAN

A

AA

AAA

AAAA

A

AA

AAA

A

AA

A

RECURSION FIRST ALTERNATE as first component, QUICKSCAN

AAAA

AAA

AA

A

AAA

AA

A

AA

A

A

recursion FIRST ALTERNATE as second component, QuickScan

AAAA

AAA

AA

A

AAA

AA

A

AA

A

A

NOW FULLSCAN MODE:::::

RECURSION SECOND ALTERNATE as Second component

A

AA

AAA

AAAA

A

AA

AAA

A

AA

A

Recursion SECOND ALTERNATE as First component

A

AA

AAA

AAAA