BAS(I)                       5/15/74                       BAS(I)


     bas - basic


     bas [ file ]


     Bas is a dialect of Basic.  If a file argument is  provided,

     the  file is used for input before the console is read.  Bas

     accepts lines of the form:


        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:


          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.


          Return to system level.

     draw expression expression expression

          A line is drawn on the Tektronix 611 display `/dev/vt0'

          from  the  current  display  position  to  the  XY  co-

          ordinates specified by the first two expressions.   The

          scale  is  zero  to one in both X and Y directions.  If

          the third expression is zero, the  line  is  invisible.

          The current display position is set to the end point.

     display list

          The list of expressions and strings is concatenated and

          displayed  (i.e.  printed)  on  the 611 starting at the

          current display position.  The current display position

          is not changed.


          The  name  and  current  value  of  every  variable  is



          The UNIX editor, ed, is invoked with the file argument.

          After the editor exits, this file is recompiled.


          The 611 screen is erased.

     for name = expression expression statement

     for name = expression expression



          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  expression,  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

          ... ]


          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 executed when

          the first group is not.

     list [expression [expression]]

          is used to print out the  stored  internal  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 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 returned.


          The internal statements are compiled.  The symbol table

          is  re-initialized.   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:


          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.


          A number is used to  represent  a  constant  value.   A

          number  is  written  in  Fortran  style,  and  contains

          digits, an optional decimal point, and possibly a scale

          factor consisting of an e followed by a possibly signed


     ( expression )

          Parentheses  are  used  to  alter   normal   order   of


     _ expression

          The result is the negation of the expression.

     expression operator expression

          Common functions of two arguments  are  abbreviated  by

          the two arguments 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 evaluates 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  restricted  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.  Assignment binds right  to  left,  all  other

          operators 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.



     The following is a list of builtin functions:


          is the value of the  i  -th  actual  parameter  on  the

          current level of function call.


          is the exponential function of x.


          is the natural logarithm of x.


          is the square root of x.


          is the sine of x (radians).


          is the cosine of x (radians).


          is the arctangent of x.  Its value is between -π/2  and


     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   input   and  evaluated  as  an  expression.   The

          resultant value is returned.


          is the absolute value of x.


          returns x truncated (towards 0) to an integer.


     /tmp/btm?       temporary

     b.out           save file


     Syntax errors cause the incorrect line to be typed  with  an

     underscore  where  the  parse failed.  All other diagnostics

     are self explanatory.


     Has been known to give core images.