term% cat index.txt SNOCONE(1) General Commands Manual 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 translates the concatena‐
tion of all the input files into a SNOBOL4 program, which it writes in
a.out. The first line of a.out arranges that if a.out is executed, the
SNOBOL4 interpreter 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 continued 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 comparisons. 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 predicates. 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 predi‐
cates.
| pattern value alternation.
? pattern match. Returns the part of the left operand matched by
the right operand, which must be a pattern. 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 argument fails,
and fails otherwise.
? Returns the null string if its argument succeeds, and fails oth‐
erwise.
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 iden‐
tifier 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 semicolons.
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 vari‐
able 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 expres‐
sion 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 inter‐
preter (see spitbol(1)).
BUGS
Run-time diagnostics refer to SNOBOL4 source statement numbers, not to
Snocone line numbers.
Extremely long statements can overflow the SNOBOL4 compiler's limits on
input line length.
SNOCONE(1)