term% cat index.txt BAS(1) General Commands Manual BAS(1)
NAME
bas - basic
SYNOPSIS
bas [ file ]
DESCRIPTION
Bas is a dialect of Basic. If a file argument is provided, the file is
used for input before the terminal 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 immedi‐
ate expression statement (that does not have `=' as its highest opera‐
tor) is printed. Interrupts suspend computation.
Statements have the following syntax:
expression
The expression is executed for its side effects (assignment or
function call) or for printing as described above.
comment
This statement is ignored. It is used to interject commentary in
a program.
done
Return to system level.
dump
The name and current value of every variable is printed.
edit
The UNIX editor, ed, is invoked with the file argument. After the
editor exits, this file is recompiled.
for name = expression expression statement
for name = expression expression
next
The for statement repetitively executes a statement (first form)
or a group of statements (second form) under control of a named
variable. The variable takes on the value of the first expres‐
sion, then is incremented by one on each loop, not to exceed the
value of the second expression.
goto expression
The expression is evaluated, truncated to an integer and execution
goes to the corresponding integer numbered statment. If executed
from immediate mode, the internal statements are compiled first.
if expression statement
if expression
[ else
fi
The statement (first form) or group of statements (second form) is
executed if the expression evaluates to non-zero. In the second
form, an optional else allows for a group of statements to be exe‐
cuted when the first group is not.
list [expression [expression]]
is used to print out the stored internal statements. If no argu‐
ments are given, all internal statements are printed. If one ar‐
gument is given, only that internal statement is listed. If two
arguments are given, all internal statements inclusively between
the arguments are printed.
print list
The list of expressions and strings are concatenated and printed.
(A string is delimited by " characters.)
prompt list
Prompt is the same as print except that no newline character is
printed.
return [expression]
The expression is evaluated and the result is passed back as the
value of a function call. If no expression is given, zero is re‐
turned.
run
The internal statements are compiled. The symbol table is re-ini‐
tialized. The random number generator is reset. Control is
passed to the lowest numbered internal statement.
save [expression [expression]]
Save is like list except that the output is written on the file
argument. If no argument is given on the command, b.out is used.
Expressions have the following syntax:
name
A name is used to specify a variable. Names are composed of a
letter 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 writ‐
ten in Fortran style, and contains digits, an optional decimal
point, and possibly a scale factor consisting of an e followed by
a possibly signed exponent.
( expression )
Parentheses are used to alter normal order of evaluation.
_ expression
The result is the negation of the expression.
expression operator expression
Common functions of two arguments are abbreviated by the two argu‐
ments separated by an operator denoting the function. A complete
list of operators is given below.
expression ( [expression [ , expression] ... ] )
Functions of an arbitrary number of arguments can be called by an
expression followed by the arguments in parentheses separated by
commas. The expression evaluates to the line number of the entry
of the function in the internally stored statements. This causes
the internal statements to be compiled. If the expression evalu‐
ates negative, a builtin function is called. The list of builtin
functions appears below.
name [ expression [ , expression ] ... ]
Each expression is truncated to an integer and used as a specifier
for the name. The result is syntactically identical to a name.
a[1,2] is the same as a[1][2]. The truncated expressions are re‐
stricted to values between 0 and 32767.
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,
& | & (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 re‐
lation. 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(i) is the value of the i -th actual parameter on the current level
of function call.
exp(x) is the exponential function of x.
log(x) is the natural logarithm of x.
sqr(x) is the square root of x.
sin(x) is the sine of x (radians).
cos(x) is the cosine of x (radians).
atn(x) is the arctangent of x. Its value is between -π/2 and π/2.
rnd( ) is a uniformly distributed random number between zero and one.
expr( )
is the only form of program input. A line is read from the in‐
put and evaluated as an expression. The resultant value is re‐
turned.
abs(x) is the absolute value of x.
int(x) returns x truncated (towards 0) to an integer.
FILES
/tmp/btm? temporary
b.out save file
/bin/ed for edit
DIAGNOSTICS
Syntax errors cause the incorrect line to be typed with an underscore
where the parse failed. All other diagnostics are self explanatory.
BUGS
Has been known to give core images.
Catches interrupts even when they are turned off.
BAS(1)