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penpen wrote: ↑

29 Mar 2018 19:03

You could implement a mathematical function as proposed by Aacini:
viewtopic.php?f=3&t=6744.

A little math library is created by einstein1969:
viewtopic.php?f=3&t=5819.

Then you should simplify your task (reduce the needed helper functions; compute a value in all if-cases) and then create a formula that computes what you need; a possibility:

Code: Select all

@echo off
setlocal enableExtensions enableDelayedExpansion
set /a "pos.x=10, width=5, vel.x=-12"

set "LssZero(x)=(-((x)>>31))"

:: short explaination
:: 1. "pos.x > width" == "0 > (width-pos.x)" == "(width-pos.x)<0"
:: 2. "if (pos.x > width || pos.x < 0) { vel.x *= -1; }"
:: == "if (pos.x > width || pos.x < 0) { vel.x *= -1; } else { vel.x *= 1; }"
:: == "vel.x *= (pos.x > width || pos.x < 0) ? -1 : 1;"
:: == "vel.x *= ( (pos.x > width || pos.x < 0) ? -2 : 0 )+1;"
:: == "vel.x *= ( (pos.x > width || pos.x < 0) ? -1 : 0 )*2+1;"
:: == "vel.x *= -( (pos.x > width || pos.x < 0) ? 1 : 0 )*2+1;"
:: == "vel.x *= (-( (pos.x > width || pos.x < 0) ? 1 : 0 )<<1)+1;"
:: == "vel.x *= (-(((pos.x > width) ? 1 : 0)|((pos.x < 0) ? 1 : 0))<<1)+1;"
:: == " vel.x *= (-((((width-pos.x)<0) ? 1: 0)|((pos.x < 0) ? 1: 0))<<1)+1;"
set /a "vel.x *= (-(%LssZero(x):x=width-pos.x%|%LssZero(x):x=pos.x%)<<1)+1"

set "vel.x"
goto :eof

penpen

aGerman wrote: ↑

30 Mar 2018 08:32

Code: Select all

@echo off &setlocal EnableDelayedExpansion

REM ----- return false=0 or true=1 -----
set "LSS(x,y)=(((x-y)>>31)&1)"
set "LEQ(x,y)=((~(y-x)>>31)&1)"
set "GTR(x,y)=(((y-x)>>31)&1)"
set "GEQ(x,y)=((~(x-y)>>31)&1)"
set "EQU(x,y)=(((~(y-x)>>31)&1)&((~(x-y)>>31)&1))"
set "NEQ(x,y)=((((x-y)>>31)&1)|(((y-x)>>31)&1))"
set "AND(b1,b2)=(b1&b2)"
set "OR(b1,b2)=(b1|b2)"

REM -----(true) ? value1 : value2
set "TERN(bool,v1,v2)=((bool*v1)|((~bool&1)*v2))"


REM Example
set /a "a=-1, b=4, c=-12"

REM (a > b || a < 0) ? c *= -1 : c
set /a "x=a, y=b, b1=%GTR(x,y)%,   y=0, b2=%LSS(x,y)%,   bool=%OR(b1,b2)%,   v1=c*-1, v2=c, c=%TERN(bool,v1,v2)%"
echo %c%

pause

I refrained from using logical NOT (!) in case delayed expansion matters.

Steffen

IcarusLives wrote: ↑

29 Mar 2018 19:32

My problem now lies with HOW do I write such a function? (The actual maths)? In the %getDistance% macro I posted above, it does contain somewhat of an "if" because it checks for the larger integer, but I don't know how it does that..

IcarusLives wrote: ↑

30 Mar 2018 09:50

my problem is now solved!!

penpen wrote: ↑

30 Mar 2018 10:46

IcarusLives wrote: ↑

29 Mar 2018 19:32

My problem now lies with HOW do I write such a function? (The actual maths)? In the %getDistance% macro I posted above, it does contain somewhat of an "if" because it checks for the larger integer, but I don't know how it does that..

IcarusLives wrote: ↑

30 Mar 2018 09:50

my problem is now solved!!

I have posted the complete creation of that exemplary function, so i'm unsure about what is the problematic part exactly, and why it now is solved.

Actually i assume that it may be have been unclear why "(-((x)>>31))" is the same as "(x < 0) ? 1 : 0", so i want to add that:
The "set/A" command internally uses a 32 bit signed integer datatype (signed integer means that the representation of the stored number is in two's complement). In Java and other languages this datatype is referred to as "int".
A characteristic of this reprasentation is that every bit with index >= 32 of an int is "1" if this int is negative, else "0" (but it isn't stored explicitely, because you only have 32 bits available).

When performing an "arithmetic right shift" (>>) all bits of an int value are moved to the right a given number of bit positions including the not explicitely stored bits.
Therefore if you shift a given number (n) 31 times ("x>>31"), then the result is either "11111111111111111111111111111111" (which is the representation of "-1") for negative numbers, else "00000000000000000000000000000000" (which is "0").
Negating the above result (and adding parentheses around the "x" and the result to protect against odd sideeffects) gives you the "LssZero(x)" function.

The functions aGerman has posted, are also fiddling with the bit representation of the given int numbers to compute their result.

penpen

aGerman wrote: ↑

30 Mar 2018 08:32

Code: Select all

@echo off &setlocal

REM ----- return 0 if false or 1 if true -----
set "LSS(x,y)=(((x-y)>>31)&1)"                     &REM <
set "LEQ(x,y)=((~(y-x)>>31)&1)"                    &REM <=
set "GTR(x,y)=(((y-x)>>31)&1)"                     &REM >
set "GEQ(x,y)=((~(x-y)>>31)&1)"                    &REM >=
set "EQU(x,y)=(((~(y-x)>>31)&1)&((~(x-y)>>31)&1))" &REM ==
set "NEQ(x,y)=((((x-y)>>31)&1)|(((y-x)>>31)&1))"   &REM !=

REM ----- values of b1 and b2 have to be either 0 or 1 -----
REM ----- return 0 if false or 1 if true -----
set "AND(b1,b2)=(b1&b2)"                           &REM &&
set "OR(b1,b2)=(b1|b2)"                            &REM ||

REM ----- ternary operation: return_value = (bool) ? value1_if_true : value2_if_false -----
REM ----- value of bool has to be either 0 or 1 -----
REM ----- returns v1 if bool=1 or v2 if bool=0 -----
set "TERN(bool,v1,v2)=((bool*v1)|((~bool&1)*v2))"  &REM ?:


REM Examples for calculations of (a > b || a < 0) ? c * -1 : c
set /a "a=-1, b=-3, c=-5"
call :calc

set /a "a=-1, b=3, c=-5"
call :calc

set /a "a=1, b=-3, c=-5"
call :calc

set /a "a=1, b=3, c=-5"
call :calc

pause
exit /b


:calc
setlocal
<nul set /p "=c = (%a% > %b% || %a% < 0) ? %c% * -1 : %c%" &echo(
set /a "x=a, y=b, b1=%GTR(x,y)%,   y=0, b2=%LSS(x,y)%,   bool=%OR(b1,b2)%,   v1=c*-1, v2=c, c=%TERN(bool,v1,v2)%"
echo c = %c%
echo ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
endlocal &exit /b

I refrained from using logical NOT (!) in case delayed expansion matters.

Steffen

b1 = 1
b2 = 1

then bool = 1

But if what's in my head is correct, then XOR would return BOOL= 0 during this case.

set "XOR(b1,b2)=((b1+b2)&1)"

set "XOR(b1,b2)=(b1^b2)"