SNOCONE(1) SNOCONE(1)
NAME
snocone - snobol with syntactic sugar
SYNOPSIS
snocone file ...
DESCRIPTION
Snocone is a programming language, syntactically similar to
C, that compiles into SNOBOL4. The Snocone compiler trans-
lates the concatenation of all the input files into a SNO-
BOL4 program, which it writes in a.out. The first line of
a.out arranges that if a.out is executed, the SNOBOL4 inter-
preter will automatically be invoked.
A synopsis of the Snocone syntax follows.
Lexical conventions
Everything after the first # on an input line is
ignored.
Statements normally end at the end of the line. If
the last character on a line is an operator, open
parenthesis or bracket, or comma, the statment is con-
tinued on the next line.
Spaces generally follow C conventions.
Binary operators (grouped by decreasing precedence):
$ . conditional and immediate pattern value assignment, as
in SNOBOL4
^ power; right-associative as in SNOBOL4
* / % multiplication, division, remainder; unlike SNOBOL4,
all have the same precedence.
+ - addition, subtraction
< > <= >= == != :<: :>: :<=: :>=: :==: :!=:
comparison operators; the ones surrounded by colons do
character comparisons, the others do numeric compar-
isons. These operators behave as SNOBOL4 predicates:
they return the null string if the indicated condition
is true, and fail if it is false.
&& concatenation; evaluates its right operand only after
its left operand has been successfully evaluated. It
therefore acts as logical and when applied to predi-
cates. The null string may be concatenated to any
value.
|| the value of the left operand if possible, otherwise
the value of the right operand. Behaves as logical or
when applied to predicates.
| pattern value alternation.
? pattern match. Returns the part of the left operand
matched by the right operand, which must be a pattern.
SNOCONE(1) SNOCONE(1)
May be used on the left of an assignment if the left
operand is appropriate. Right-associative.
= assignment
Unary operators; all map to their SNOBOL4 equivalents and
have the same (highest) precedence.
+ The numeric equivalent of its argument.
- The numeric equivalent of its argument, with the sign
reversed.
* Unevaluated expression, as in SNOBOL4.
$ If v is a value of type name, then $v is the variable
of that name.
@ Pattern matching cursor assignment.
~ Logical negation: returns the null string if its argu-
ment fails, and fails otherwise.
? Returns the null string if its argument succeeds, and
fails otherwise.
Returns a value of type
name that refers to its (lvalue) argument.
Statements
Statements may be prefixed by one or more labels. A label
is an identifier followed by a colon, as in C. All labels
are global: it is a good idea to begin labels in procedures
with the name of the procedure.
expression
The given expression is evaluated for its side effects.
{ statement ... }
The statements are executed sequentially.
if (expression) statement [ else statement ]
If evaluation of the expression succeeds, the first
statement is executed. Otherwise, the second
statement, if any, is executed. An else belongs to the
closest unmatched if.
while (expression) statement
The statement is executed repeatedly, as long as the
expression can be successfully evaluated.
do statement while (expression)
Like the while statement, except that the statement is
executed once before the first time the expression is
evaluated.
for (e1, e2, e3) statement
As in C, except that commas are used instead of semi-
colons.
SNOCONE(1) SNOCONE(1)
return [expression]
returns the value of the expression from the current
function. If expression fails or is missing, the value
returned is that of the variable with the same name as
the function. If that variable was never set, the
function returns the null string.
nreturn [expression]
The expression must be the name of a variable. That
variable is returned from the current function as an
lvalue. If the expression fails or is missing, the
variable with the same name as the function must have
been set to the name of a variable.
freturn
The current function returns failure.
goto label
Transfer control to the given label.
Procedures may not be textually nested, but may be recursive
and may call each other in forward references. The general
form of a procedure declaration is:
procedure name (args) locals { statement ... }
The args and locals are lists of variable names, separated
by commas. Since Snocone is a dynamically typed language,
further declarations are not necessary. Although procedures
are not textually nested, names are dynamically scoped: a
procedure can reference the local variables and parameters
of its caller as if they were global variables.
Assigning a (string) value to the variable output causes
that value to be written as a single line on the standard
output. Accessing the variable input causes a line to be
read from the standard input. The access fails at end of
file. Accessing or assigning to the variable terminal
causes a line to be read from or written to the standard
error file. Other input-output is as implemented by the
Macrospitbol interpreter (see spitbol(1)).
BUGS
Run-time diagnostics refer to SNOBOL4 source statement num-
bers, not to Snocone line numbers.
Extremely long statements can overflow the SNOBOL4
compiler's limits on input line length.