Optimize a string reversal

[acantor]

For a script I am developing, I need to reverse the order of characters. For example, "12345"  needs to transform into "54321". Macro Express does not appear to have an instruction for reversing strings, so I wrote a script that does just that.

 

I would be curious to know if there are ways to make a script like this run faster. It's quick for strings consisting of a few dozen or hundred characters, but noticeably slower when the string contains thousands of characters.

 

(This test script is set to use "0123456789" as its input.)

 

// String reverse
//      %Text% = String before processing
//      %Result% = String after processing
Variable Set String %Text% to "0123456789"
Variable Set String %Result% to ""
 
//      %Len% = Number of characters in %Text%
//      %Start% = Starting position of the character to copy. (Begin with the last one)
Variable Set Integer %Len% to the length of variable %Text%
Variable Set Integer %Start% to %Len%
 
// Begin by copying the final character in %Text%. Next time, copy the second last character, etc.
// Each time, append the character, %Char%, to the end of %Result%
Repeat Start (Repeat %Len% times)
  Variable Modify String: Copy part of text in %Text% starting at %Start% and 1 characters long to %Char%
  Variable Modify String %Result%: Append Text (%Char%)
  Variable Modify Integer %Start%: Decrement
End Repeat
 
Text Box Display: Result

<COMMENT Value="String reverse"/>
<COMMENT Value="     %Text% = String before processing"/>
<COMMENT Value="     %Result% = String after processing"/>
<VARIABLE SET STRING Option="\x00" Destination="%Text%" Value="0123456789" NoEmbeddedVars="FALSE"/>
<VARIABLE SET STRING Option="\x00" Destination="%Result%" NoEmbeddedVars="FALSE"/>
<COMMENT/>
<COMMENT Value="     %Len% = Number of characters in %Text%"/>
<COMMENT Value="     %Start% = Starting position of the character to copy. (Begin with the last one)"/>
<VARIABLE SET INTEGER Option="\x0D" Destination="%Len%" Text_Variable="%Text%"/>
<VARIABLE SET INTEGER Option="\x00" Destination="%Start%" Value="%Len%"/>
<COMMENT/>
<COMMENT Value="Begin by copying the final character in %Text%. Next time, copy the second last character, etc."/>
<COMMENT Value="Each time, append the character, %Char%, to the end of %Result%"/>
<REPEAT START Start="1" Step="1" Count="%Len%" Save="FALSE"/>
<VARIABLE MODIFY STRING Option="\x09" Destination="%Char%" Variable="%Text%" Start="%Start%" Count="1" NoEmbeddedVars="FALSE"/>
<VARIABLE MODIFY STRING Option="\x06" Destination="%Result%" Value="%Char%" NoEmbeddedVars="FALSE"/>
<VARIABLE MODIFY INTEGER Option="\x08" Destination="%Start%"/>
<END REPEAT/>
<COMMENT/>
<TEXT BOX DISPLAY Title="Result" Content="{\\rtf1\\ansi\\ansicpg1252\\deff0\\deflang1033{\\fonttbl{\\f0\\fnil\\fcharset0 Tahoma;}{\\f1\\fnil Tahoma;}}\r\n\\viewkind4\\uc1\\pard\\f0\\fs40 %Result%\\f1 \r\n\\par }\r\n" Left="Center" Top="Center" Width="278" Height="200" Monitor="0" OnTop="TRUE" Keep_Focus="TRUE" Mode="\x00" Delay="0"/>
<END REPEAT _ENABLED="FALSE"/>
<TEXT BOX DISPLAY Title="Done" Content="{\\rtf1\\ansi\\ansicpg1252\\deff0\\deflang1033{\\fonttbl{\\f0\\fnil Tahoma;}}\r\n\\viewkind4\\uc1\\pard\\f0\\fs20 \r\n\\par }\r\n" Left="Center" Top="Center" Width="278" Height="200" Monitor="0" OnTop="TRUE" Keep_Focus="TRUE" Mode="\x00" Delay="0" _ENABLED="FALSE"/>

 

[terrypin]

 

Hi Alan,

 

Saw this just before dashing out so have not yet tried your script. I expect this old one of mine will be much slower, designed for relatively short strings. Note that the Variable Restore is disabled. This was intended as a submacro.

 

Later...

 

Terry

 

EDIT: Back home and tested both. Indistinguishable difference in performance until I got to 5,000 random characters when mine seemed very slightly faster.

 

 

Variable Restore: Restore Text Variables // Restore Input from a previous macro
// Disable the next TBD if you want silent running.
Variable Set String %Input%: Prompt
Variable Set Integer %Length% to the length of variable %Input%
Repeat Start (Repeat %Length% times)
  Variable Modify String: Copy part of text in %Input% starting at %Index% and 1 characters long to %Char%
  Variable Modify String %Output%: Append Text String Variable (%Char%)
End Repeat
// Disable the next TBD if you want silent running.
Text Box Display: Full Input string reversed


<VARIABLE RESTORE Option="\x01" _ENABLED="FALSE" _COMMENT="Restore Input from a previous macro"/>
<COMMENT Value="Disable the next TBD if you want silent running."/>
<VARIABLE SET STRING Option="\x01" Destination="%Input%" Prompt="Please input a string of characters" Mask="FALSE" OnTop="FALSE" Left="Center" Top="Center" Monitor="0"/>
<VARIABLE SET INTEGER Option="\x0D" Destination="%Length%" Text_Variable="%Input%"/>
<REPEAT START Start="%Length%" Step="-1" Count="%Length%" Save="TRUE" Variable="%Index%"/>
<VARIABLE MODIFY STRING Option="\x09" Destination="%Char%" Variable="%Input%" Start="%Index%" Count="1" NoEmbeddedVars="FALSE"/>
<VARIABLE MODIFY STRING Option="\x07" Destination="%Output%" Variable="%Char%" NoEmbeddedVars="FALSE"/>
<END REPEAT/>
<COMMENT Value="Disable the next TBD if you want silent running."/>
<TEXT BOX DISPLAY Title="Full Input string reversed" Content="{\\rtf1\\ansi\\ansicpg1252\\deff0\\deflang1033{\\fonttbl{\\f0\\fnil\\fcharset0 Tahoma;}{\\f1\\fnil Tahoma;}}\r\n\\viewkind4\\uc1\\pard\\f0\\fs16 %Output%\\f1 \r\n\\par }\r\n" Left="Center" Top="Center" Width="278" Height="200" Monitor="0" OnTop="TRUE" Keep_Focus="TRUE" Mode="\x00" Delay="0"/>

 

[rberq]

A great puzzle.  I can see I will be thinking about it all day, and greatly annoying my wife by ignoring her and everything else.  If I can invent anything, I'll reply again.  🙂

[acantor]

Terry,

 

Your solution is cleaner and more elegant than mine, and I can imagine it might run a bit faster. Thank you for posting!

 

It's interesting, educational, and entertaining to develop one's own string manipulation tools. I was going to write Insight and request they add features like reverse, pre-pend to a string (to complement the already-existing append). But if Insight had added these features in the past, I wouldn't have taken the time to learn how to build them myself!

[terrypin]

Alan,

 

Yes, absorbing! On the downside,  I can't immediately recall why I wrote that 🙂