path: root/static/unix-v10/man1/snocone.1

.TH SNOCONE 1
.CT 1 prog_other
.SH NAME
snocone \- snobol with syntactic sugar
.SH SYNOPSIS
.B snocone
.I file ...
.SH DESCRIPTION
.I Snocone
is a programming language, syntactically
similar to C, that compiles into 
.SM SNOBOL4.
The Snocone compiler translates the concatenation of all
the input files into a 
.SM SNOBOL4
program, which it writes in
.FR a.out .
When
.F a.out
is executed, the 
.SM SNOBOL4
interpreter will automatically be invoked.
A synopsis of Snocone syntax follows.
.SS Lexical conventions
.br
Everything after the first unquoted
.L #
on an input line is ignored.
.br
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 statement is
continued on the next line.
.SS "Binary operators, \fRgrouped by decreasing precedence"
.TP
.B []
Array and table indexing (denoted in 
.SM SNOBOL4
by
.LR <> ).
.PD 0
.TP
.B $ .
conditional and immediate pattern value assignment,
as in 
.SM SNOBOL4
.TP
.B ^
power; right-associative as in 
.SM SNOBOL4
.TP
.B * / %
multiplication, division, remainder;
unlike 
.SM SNOBOL4,
all have the same precedence.
.TP
.B + -
addition, subtraction
.TP
.B
<  >  <=  >=  ==  !=  :<:  :>:  :<=:  :>=:  :==:  :!=:
comparison operators; the ones surrounded by colons
compare strings, the others compare numbers.
These operators behave as 
.SM SNOBOL4
predicates: they return
the null string if the condition is true,
and fail if it is false.
.TP
.B &&
concatenation;
evaluates its right operand
only after its left operand has been successfully
evaluated.
It therefore acts as logical
.I and
when applied to predicates.
The null string may be concatenated to any value.
.TP
.B |\^|
the value of the left operand if possible, otherwise
the value of the right operand.
.TP
.B |
pattern value alternation.
.TP
.B ?
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.
.TP
.B =
assignment
.PD
.SS Unary operators
.TP
.B +
The numeric equivalent of its argument.
.PD 0
.TP
.B -
The numeric equivalent of its argument, with the sign reversed.
.TP
.B *
Unevaluated expression, as in 
.SM SNOBOL4.
.TP
.B $
If
.I v
is a value of type
.BR name ,
then
.BI $ v
is the variable of that name.
.TP
.B @
Pattern matching cursor assignment.
.TP
.B ~
Logical negation: returns the null string if its argument
fails, and fails otherwise.
.TP
.B ?
Returns the null string if its argument succeeds,
and fails otherwise.
.TP
.B \&.
Returns a value of type
.B name
that refers to its (lvalue) argument.
.PD
.SS Statements
.PP
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 prefix labels in procedures
with the name of the procedure.
.TP
.I expression
The given
.I expression
is evaluated for its side effects.
.TP
.BI { " statement ... " }
The
.I statements
are executed sequentially.
.TP
.BI "if (" expression ) " statement \fR[ " else " statement\fR ]"
If evaluation of the
.I expression
succeeds, the first
.I statement
is executed.
Otherwise, the second
.IR statement ,
if any, is executed.
An
.I else
belongs to the closest unmatched
.BR if .
.TP
.BI "while (" expression ") " statement
The
.I statement
is executed repeatedly, as long as the
.I expression
can be successfully evaluated.
.TP
.BI "do " statement " while (" expression )
Like the
.B while
statement, except that the
.I statement
is executed once before the first time the
.I expression
is evaluated.
.TP
.B
for (\fIe1\fP, \fIe2\fP, \fIe3\fP) \fIstatement\fP
As in C, except that commas are used instead of semicolons.
.TP
.BR return " [\fIexpression\fP]"
returns the value of the
.I expression
from the current function.
If
.I 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.
.TP
.BR nreturn " [\fIexpression\fP]"
The
.I expression
must be the name of a variable.
That variable is returned from the current
function as an lvalue.
If the
.I expression
fails or is missing, the variable with the
same name as the function must have been set to the
name of a variable.
.TP
.B freturn
The current function returns failure.
.TP
.BI goto " label"
Transfer control to the given
.I label.
.HP Procedures
.PP
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:
.IP
.B
procedure \fIname\fP (\fIargs\fP) \fIlocals\fP { \fIstatement ... \fP}
.PP
The
.I args
and
.I 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.
.HP Input-Output
.PP
Assigning a (string) value to the variable
.L output
causes that value to be written as a single line on the
standard output.
Accessing the variable
.L input
causes a line to be read from the standard input.
The access fails at end of file.
Accessing or assigning to the variable
.L 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
.IR langs (1).
.SH SEE ALSO
A. R. Koenig,
`The Snocone Programming Language',
this manual, Volume 2
.br
.IR langs (1)
.SH BUGS
Run-time diagnostics refer to 
.SM SNOBOL4
source statement numbers,
not to Snocone line numbers.
.br
Extremely long statements can overflow the 
.SM SNOBOL4
compiler's
limits on input line length.