Code Generation for Constant Multiplication/Division

By Nikolai Golovchenko. See https://www.golovchenko.org/home/constdivmul for a working online form and source code.

See:

• Expression Evaluator

See also:

• PIC Math
• General Math Methods
• Mark Sullivan's evaluation of infix expression in PIC code
• Interactive Digital Filter Design - IIR (Butterworth / Bessel / Chebyshev, Resonator, Proportional-Integral) anf FIR (Raised Cosine, Hilbert Transformer)

Questions:

• danmiller0@yahoo.com asks:

  IS there a way of getting this code generation program in a simple windows program? It would be handy for when I am working from a workstation that does not have internet access.

  The program does have a command line mode (not GUI) so it could be used locally... If there is enough interest, I could sell offline versions. Perhaps this would help to support the site?

Comments:

• jd@xtremepowersystems.net " I would definitely buy a version that supported the PIC18 parts, so that the MULWF instruction was used whenever possible!
  "
• ebp1@telus.net

  When used for division, except in cases where the sum of the terms exactly equals the divisor (e.g. divisor is 8/3 = 2.6666667), the computed quotient will always be slightly smaller than the actual quotient. Rounding can be helpful, particularly with small quotients. Before the final shift, simply examine the highest-order bit that would be shifted out and add it after the final shift.
  e.g. if the last shifting is 4 places and the bits that would be shifted out are 1xxx, add 1 after the last shift.
  Try this for 9 divided by 3, using 7 terms. Without rounding, the quotient will be 2. Rounding "fixes" that.

• pic@harry-arends.nl " When i use the code to make a routine that does arg*10 is works wel but when i want to make a divider using 1/10 is produces some useless code." James Newton replies: Please do not enter "1/10". Instead enter the RESULT of 1/10 which is ".1". Given .1, it generates very nice code for dividing by 10.

Interested: