OpenEuphoria

Re: absolute function

• Posted by mattlewis (admin) Mar 24, 2011
• 3561 views

function abs(integer x) 
  return and_bits(-(x<0), -x) + and_bits(-(x>0), x) 
end function 

Pretty clever. I haven't tested, but for integers, a simple if statement should be faster:

function simple_abs( integer x ) 
	if x >= 0 then 
		return x 
	else 
		return -x 
	end if 
end function 

If you look at the IL code for the two of them:

SubProgram [/home/matt/eu/test/bill.ex-abs:00146]  [x:148] 
	STACK SPACE: 9 
	Required:    9 
 
        [/home/matt/eu/test/bill.ex:1]  (1) 
     1: 096 148                          # INTEGER_CHECK: [x:148] 
 
        [/home/matt/eu/test/bill.ex:2]  (2) 
     3: 001 148 143 149                  # LESS: [x:148], [LIT 0:143] => [_temp_:149] 
     7: 012 149 150                      # UMINUS: [_temp_:149] => [_temp_:150] 
    10: 012 148 151                      # UMINUS: [x:148] => [_temp_:151] 
    13: 056 150 151 152                  # AND_BITS: [_temp_:150], [_temp_:151] => [_temp_:152] 
    17: 006 148 143 153                  # GREATER: [x:148], [LIT 0:143] => [_temp_:153] 
    21: 012 153 154                      # UMINUS: [_temp_:153] => [_temp_:154] 
    24: 056 154 148 155                  # AND_BITS: [_temp_:154], [x:148] => [_temp_:155] 
    28: 011 152 155 156                  # PLUS: [_temp_:152], [_temp_:155] => [_temp_:156] 
    32: 208 150                          # DEREF_TEMP: [_temp_:150]  
    34: 208 151                          # DEREF_TEMP: [_temp_:151]  
    36: 208 152                          # DEREF_TEMP: [_temp_:152]  
    38: 208 154                          # DEREF_TEMP: [_temp_:154]  
    40: 208 155                          # DEREF_TEMP: [_temp_:155]  
    42: 028 146 147 156                  # RETURNF: [_temp_:156] block[147] 
    46: 043                              # BADRETURNF: 
End SubProgram [abs:00146] 
 
SubProgram [/home/matt/eu/test/bill.ex-simple_abs:00157]  [x:159] 
	STACK SPACE: 3 
	Required:    3 
 
        [/home/matt/eu/test/bill.ex:5]  (5) 
     1: 096 159                          # INTEGER_CHECK: [x:159] 
 
        [/home/matt/eu/test/bill.ex:6]  (6) 
     3: 120 159 143 13                   # GREATEREQ_IFW [x:159] > [LIT 0:143] goto 0007 else goto 0013 
 
        [/home/matt/eu/test/bill.ex:7]  (7) 
     7: 028 157 158 159                  # RETURNF: [x:159] block[158] 
 
        [/home/matt/eu/test/bill.ex:8]  (8) 
    11: 023 20                           # ELSE goto 0020 
 
        [/home/matt/eu/test/bill.ex:9]  (9) 
    13: 012 159 163                      # UMINUS: [x:159] => [_temp_:163] 
    16: 028 157 158 163                  # RETURNF: [_temp_:163] block[158] 
    20: 043                              # BADRETURNF: 
End SubProgram [simple_abs:00157] 

There are lots of operations created, and several temps.

Matt