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--- using_20the_20fscale_20instruction [2018/04/01 14:37] – 86.143.37.84
+++ using_20the_20fscale_20instruction [2024/01/05 00:21] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 =====Using the fscale instruction=====
-//by Tony Tooth, January 2016//\\ \\  Randall Hyde's book "The Art of Assembly Language" omits to cover or even mention the fscale instruction in the main text or in the index, although it is in his Table B-2: Floating Point Instruction Set.\\ \\  fscale (I discovered only late in 2015 - after more than 10 years experience programming in assembly language) is a fast and efficient way to implement the exponential function in assembly language. The way I did this hitherto was incredibly cumbersome. I have written a simple sub-routine in assembly language to illustrate the use of fscale. Note that my illustrative routine does not check for out-of-bounds numbers.\\ \\
+//by Tony Tooth, January 2016. Edited by Tony Tooth April 2018//\\ \\  Randall Hyde's book "The Art of Assembly Language" omits to cover or even mention the fscale instruction in the main text or in the index, although it is in his Table B-2: Floating Point Instruction Set.\\ \\  fscale (I discovered only late in 2015 - after more than 10 years experience programming in assembly language) is a fast and efficient way to implement the exponential function in assembly language. The way I did this hitherto was incredibly cumbersome. I have written a simple sub-routine in assembly language to illustrate the use of fscale. Note that my illustrative routine does not check for out-of-bounds numbers.
-      def fn_fractpower(num, pow)
+<code bb4w>
-      local pass&, res
+      DEF FN_fractpower(num, pow)
+      LOCAL pass&, res
-      private Fract%, P%
+      PRIVATE Fract%, P%
       num = 1.0*num : pow = 1.0*pow
-      if Fract% = 0 then
+      IF Fract% = 0 THEN
-        dim P% 1000
+        DIM P% 1000
-        for pass& = 0 to 2 step 2
+        FOR pass& = 0 TO 2 STEP 2
           [opt pass&
           .Fract%
@@ Line 37: / Line 38: @@
           ret
           ]
-        next pass&
+        NEXT pass&
-      endif
+      ENDIF
-      call Fract%
+      CALL Fract%
       = res
+</code>
-\\ //Edit by Richard Russell, January 2016://\\ \\  An alternative way of computing the exponential function in BB4W v6 assembly language is to call the internal EXP routine, which is exposed via the **@fn%()** jump table, as follows (it uses **fscale** internally):\\ \\
+//Edit by Richard Russell, January 2016://\\ \\  An alternative way of computing the exponential function in BB4W v6 assembly language is to call the internal EXP routine, which is exposed via the **@fn%()** jump table, as follows (it uses **fscale** internally):
+<code bb4w>
         @% = &1415
         REPEAT
@@ Line 73: / Line 77: @@
         CALL X%
         = y
+</code>