XML CO538 Anonymous Questions and Answers Keyword Index

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Keyword reference for libraries

Question 80 (2006):

Submission reference: IN1111

Is inverse tan anywhere in the libraries?

Answer 80:

Yes:

    REAL32 FUNCTION TAN (VAL REAL32 v)     -- tangent (single precision)
    REAL64 FUNCTION DTAN (VAL REAL64 v)    -- tangent (double precision)

    REAL32 FUNCTION ATAN (VAL REAL32 v)    -- anti-tangent (single precision)
    REAL64 FUNCTION DATAN (VAL REAL64 v)   -- anti-tangent (double precision)

To use them, you'll need to import and link the relevant math library:

    #USE "dblmath.lib"
    #USE "snglmath.lib"

By the way, you can quickly find these functions by grepping the Inmos math-library sources, which are in KRoC distributions. There's not much documentation unfortunately. All the trig functions work in radians, of course, not in degrees. For example, ATAN(1) is pi/4 radians (i.e. 45 degrees).

To link in the above libraries, you must extend the occPlug "Libraries:" option – currently you're probably using "course". To do this:

• close your occPlug window, if open;

• in the jEdit wondow, select "Plugins" / "Plugin Options" ... then "Plugins" / "occPlug" / "Libraries" ... make the RHS window wide enough to see the "Collection Name" and "Collection Options" columns ... click the big "+" symobol (bottom-left) ... enter a name (e.g. "course-maths") and click "OK" ... double click on the "Collection Options" side of the new "course-maths" collection ... delete the "<add libraries>" text and replace it with:

      -l course -l occama -l occamutl -l snglmath  -l dblmath
  

• Now, open the occPlug window, select "course-maths" from the "Libraries:" option and you are all set to compile and run code using ATAN etc.

    #USE "dblmath.lib"
    #USE "snglmath.lib"

    #INCLUDE "consts.inc"
    #USE "course.lib"

    PROC atan (CHAN BYTE keyboard?, screen!, error!)
      SEQ
        REAL32 x, y:
        SEQ
          x := 1.0
          y := ATAN (x)
          VAL INT pi.1000 IS INT ROUND (4000.0 * y):
          SEQ
            out.string ("pi**1000 = ", 0, screen!)
            out.int (pi.1000, 0, screen!)
            out.string ("*c*n", 0, screen!)
        REAL64 x, y:
        SEQ
          x := 1.0
          y := DATAN (x)
          VAL INT pi.1000 IS INT ROUND (4000.0 * y):
          SEQ
            out.string ("pi**1000 = ", 0, screen!)
            out.int (pi.1000, 0, screen!)
            out.string ("*c*n", 0, screen!)
    :

which produces:

    pi*1000 = 3142
    pi*1000 = 3142

which are the correct answers, :).

Keywords: libraries

Question 78 (2006):

Submission reference: IN1107

How do I get square root in occam?

Answer 78:

Something like this:

  REAL64 x:
  SEQ
    x := DSQRT (64.0)
    ...
    out.real64 (x, 0, 0, scr!)

or, if you're using 32-bit floats:

  REAL32 x:
  SEQ
    x := SQRT (64.0)
    ...
    out.real32 (x, 0, 0, scr!)

The two integers (0 and 0 here) specify the number of integer places and number of decimal places — 0 means "as many as required".

Keywords: coursework , libraries