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Unix Version 7 - man page for bas (v7 section 1)

BAS(1)				     General Commands Manual				   BAS(1)

       bas - basic

       bas [ file ]

       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:

	  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 exe-
       cuted.  The result of an immediate expression statement (that does not  have  `='  as  its
       highest operator) is printed.  Interrupts suspend computation.

       Statements have the following syntax:

	    The  expression is executed for its side effects (assignment or function call) or for
	    printing as described above.

	    This statement is ignored.	It is used to interject commentary in a program.

	    Return to system level.

	    The name and current value of every variable is printed.

	    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
	    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 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 corre-
	    sponding  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 state-
	    ment 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 ran-
	    dom number generator is reset.  Control is passed to  the  lowest  numbered  internal

       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 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 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,

       &  |   & (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(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 -n/2 and n/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 input and evaluated  as
	      an expression.  The resultant value is returned.

       abs(x) is the absolute value of x.

       int(x) returns x truncated (towards 0) to an integer.

       /tmp/btm? temporary
       b.out	      save file
       /bin/ed	 for edit

       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.
       Catches interrupts even when they are turned off.


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