The extension is described in Blocks a new datatype for SNOBOL4, James F. Gimpel, Communications of the ACM, Volume 15 Issue 6, June 1972, Pages 438-447.
BLOCKS were originally implemented in SNOBOL4, and then re-implemented in in SIL (the Macro SNOBOL4 SNOBOL Implementation Language).
A manual appears in the Michigan Terminal Service (MTS) SNOBOL in MTS Manual (pdf).
The following program:
* MTS Volume 9 (Sept 1975) p151
DEFINE('OUTLINE(B,DH,DW)UL,UR,LL,LR') :(OUTLINE_END)
OUTLINE
UL = UR = LL = LR = '+'
B = VER(DH) % HOR(DW) B HOR(DW) % VER(DH)
B = UL REP('-') UR %
+ IT('|') B IT('|') %
+ LL REP('-') LR
OUTLINE = FIX(B) :(RETURN)
OUTLINE_END
PRINT(OUTLINE('ABC', 5, 10))
* MTS Volume 9 (Sept 1975) p146
PRINT(OUTLINE(OUTLINE('ABC', 5, 10),,1))
Produces:
+-----------------------+ | | | | | | | | | | | ABC | | | | | | | | | | | +-----------------------+ +---------------------------+ | +-----------------------+ | | | | | | | | | | | | | | | | | | | | | | | ABC | | | | | | | | | | | | | | | | | | | | | | | +-----------------------+ | +---------------------------+And this:
N1 = NODE(OUTLINE('N1',2,4))
N2 = NODE(OUTLINE('N2',1,2))
N3 = NODE(OUTLINE('N3',3,1))
N4 = NODE(OUTLINE('N4',2,8))
VERT = '|' % '|' % '|'
B = MERGE(N1 '-----------' N2,
+ N1 % VERT % N3,
+ N2 % REP('|') % N4,
+ N3 REP('-') N4)
PRINT(B)
Produces this output:
+----------+
| | +------+
| | | |
| N1 |-----------| N2 |
| | | |
| | +------+
+----------+ |
| |
| |
| |
+----+ |
| | +------------------+
| | | |
| | | |
| N3 |--------| N4 |
| | | |
| | | |
| | +------------------+
+----+
Phil Budne resurected SNOBOL4B in CSNOBOL4 version 2.0 with files from MTS, supplied by Mike Alexander.