SNOBOL4EXT(1) | CSNOBOL4B 2.3 | March 25, 2022


snobol4ext – CSNOBOL4 extensions


This page describes extensions to the Bell Telephone Laboratories portable implementation of SNOBOL4 in snobol4(1).

Multiple ARRAY and/or TABLE index operations may appear in a row, without having to resort to use of the ELEMENT function, so long as no intervening spaces (or line continuations) appear.

Case folding
By default the compiler folds identifiers and directives to upper case, so programs can be entered in either case: see snobol4(1), -CASE in snobol4ctrl(1), &CASE in snobol4key(1).

Control lines
The following additional “control lines” are implemented: -CASE, -COPY, -BLOCKS/-NOBLOCKS, -ERROR/-NOERRORS, -EXECUTE/-NOEXECUTE, -HIDE, -INCLUDE, -LINE: See snobol4ctrl(1).

The following additional functions are implemented: ATAN(), BREAKX(), CHAR(), CHOP() COS(), DATE(), DELETE(), EXP(), FILE(), FILE_ABSPATH(), FILE_ISDIR() FREEZE(), FUNCTION(), HOST(), IO_FINDUNIT() LABEL(), LEQ(), LGE(), LLE(), LLT(), LN(), LNE(), LOG(), LPAD(), ORD(), RENAME(), REVERSE(), RPAD(), RSORT(), SET() SETEXIT(), SIN(), SORT(), SQRT(), SSET(), SUBSTR(), TAN(), THAW(), VDIFFER(): see snobol4func(1).

The following additional keywords are implemented: &CASE, &DIGITS, &ERRTEXT &FATAL, &FATALLIMIT, &FILE, &GCTIME, &GTRACE &LASTFILE, &LASTLINE, &LCASE, &LINE, &MAXINT, &PARM, &PI, &STEXEC, &UCASE: see snobol4key(1).

REAL numbers in INTEGER contexts
REAL numbers (or strings convertible to REAL) are accepted in all contexts which previously required an INTEGER (or string convertible to INTEGER). Contexts include TABLE(), ITEM(), array indices, INPUT(), OUTPUT(), SET(), keyword values, CHAR(), RPAD(), LPAD(), FIELD(), COLLECT(), DUMP(), DUPL(), OPSYN(), SUBSTR() added in CSNOBOL4 0.99.44.

Scientific notation
REAL number syntax has been expanded to allow exponents of the form: ANY('Ee') ('+' | '-' | ”) SPAN('0123456789') -- added in CSNOBOL4 0.98.

Exponential format reals need not contain a decimal point added in CSNOBOL4 0.99.44.

SPITBOL extensions
For compatibility with SNOBOL4+, certain SPITBOL extensions can be enabled and disabled using the -PLUSOPS directive. -PLUSOPS 0 or -PLUSOPS disables SPITBOL operators, while -PLUSOPS n where n is a non-zero integer enables them. SPITBOL extensions are enabled by default. Extensions controlled by PLUSOPS are as follows:

The SPITBOL scan (?) and assignment (=) operators have been added. A pattern match can appear within an expression, and returns the matched string as its value. Similarly assignment can appear in an expression, and returns the assigned value. An assignment after a scan (ie; STRING ? PATTERN = VALUE) performs a scan and replace. Assignment is right associative, and has the lowest precedence, while scan is left associative and has a precedence just higher than assignment.

The SPITBOL selection/alternative construction can be used in any expression. It consists of a comma separated list of expressions inside parentheses. The expressions are evaluated until one succeeds, and its value is returned. Abuse of this construction may result in incomprehensible code.

The type NUMERIC with CONVERT() and the removal of leading spaces from strings converted to numbers (implicitly or explicitly) are also legal when SPITBOL extensions are enabled.

TERMINAL I/O variable
The variable TERMINAL is associated with the standard error file descriptor for both input and output (replaces PUNCH variable).

TRACE() function type argument
The second argument of the TRACE() function can be abbreviated to a single letter: C (CALL), F (FUNCTION), K (KEYWORD), L (LABEL), R (RETURN), or V (VALUE) as in Macro SPITBOL.

Keyword trace
TRACE() works on &STFCOUNT keyword added in CSNOBOL4 0.99.44.

Value TRACE() on pattern match assignments
variable changes by . and $ operators are visible via value trace.


Add CSNOBOL4 version where each extension added?

Group the keywords, control lines, functions, operators together?


snobol4(1). snobol4ctrl(1), snobol4func(1), snobol4key(1).