3/15/72 BAS (I)
NAME bas -- basic
SYNOPSIS bas [ file ]
DESCRIPTION bas is a dialect of basic [1]. If a file argu-
ment is provided, the file is used for input be-
fore the console is read.
bas accepts lines of the form:
statement
integer statement
Integer numbered statements (known as internal
statements) are stored for later execution. They
are stored in sorted ascending order. Non-
numbered statements are immediately executed.
The result of an immediate expression statement
(that does not have '=' as its highest operator)
is printed.
Statements have the following syntax: (expr is
short for expression)
expr
The expression is executed for its side ef-
fects (assignment or function call) or for
printing as described above.
done
Return to system level.
for name = expr expr statement
for name = expr expr
...
next
The for statement repetitively executes a
statement (first form) or a group of state-
ments (second form) under control of a
named variable. The variable takes on the
value of the first expression, then is in-
cremented by one on each loop, not to ex-
ceed the value of the second expression.
goto expr
The expression is evaluated, truncated to
an integer and execution goes to the corre-
sponding integer numbered statment. If ex-
ecuted from immediate mode, the internal
statements are compiled first.
if expr statement
The statement is executed if the expression
evaluates to non-zero.
list [expr [expr]]
list is used to print out the stored inter-
nal statements. If no arguments are given,
all internal statements are printed. If
one argument is given, only that internal
statement is listed. If two arguments are
given, all internal statements inclusively
between the arguments are printed.
print expr
The expression is evaluated and printed.
return [expr]
The expression is evaluated and the result
is passed back as the value of a function
call.
run
The internal statements are compiled. The
symbol table is re-initialized. The random
number generator is re-set. Control is
passed to the lowest numbered internal
statement.
Expressions have the following syntax:
name
A name is used to specify a variable.
Names are composed of a letter ('a' - 'z')
followed by letters and digits. The first
four characters of a name are significant.
number
A number is used to represent a constant
value. A number is composed of digits, at
most one decimal point ('.') and possibly
a scale factor of the form e digits or e-
digits.
( expr )
Parentheses are used to alter normal order
of evaluation.
expr op expr
Common functions of two arguments are ab-
breviated by the two arguments separated by
an operator denoting the function. A com-
plete list of operators is given below.
expr ( [expr [, expr ...]] )
Functions of an arbitrary number of argu-
ments can be called by an expression fol-
lowed by the arguments in parentheses sepa-
rated by commas. The expression evaluates
to the line number of the entry of the
function in the internally stored state-
ments. This causes the internal statements
to be compiled. If the expression evalu-
ates negative, a builtin function is
called. The list of builtin functions ap-
pears below.
name [ expr [, expr ...] ]
Arrays are not yet implemented.
The following is the list of operators:
=
= is the assignment operator. The left
operand must be a name or an array element.
The result is the right operand. Assign-
ment binds right to left, all other opera-
tors bind left to right.
& |
& (logical and) has result zero if either
of its arguments are zero. It has result
one if both its arguments are non-zero. |
(logical or) has result zero if both of its
arguments are zero. It has result one if
either of its arguments are non-zero.
< <= > >= == <>
The relational operators (< less than, <=
less than or equal, > greater than, >=
greater than or equal, == equal to, <> not
equal to) return one if their arguments are
in the specified relation. They return
zero otherwise. Relational operators at
the same level extend as follows: a>b>c is
the same as a>b&b>c.
+ -
Add and subtract.
* /
Multiply and divide.
^
Exponentiation.
The following is a list of builtin functions:
arg
Arg(i) is the value of the ith actual pa-
rameter on the current level of function
call.
exp
Exp(x) is the exponential function of x.
log
Log(x) is the logarithm base e of x.
sin
Sin(x) is the sine of x (radians).
cos
Cos(x) is the cosine of x (radians).
atn
Atn(x) is the arctangent of x. (Not imple-
mented.)
rnd
Rnd() is a uniformly distributed random
number between zero and one.
expr
Expr() is the only form of program input.
A line is read from the input and evaluated
as an expression. The resultant value is
returned.
int
Int(x) returns x truncated to an integer.
FILES /tmp/btm? temporary
SEE ALSO [1] DEC-11-AJPB-D
DIAGNOSTICS Syntax errors cause the incorrect line to be
typed with an underscore where the parse failed.
All other diagnostics are self explanatory.
BUGS Arrays [] are not yet implemented. In general,
program sizes, recursion, etc are not checked,
and cause trouble.
OWNER ken