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== Usage ==
This module is designed as an way to escape strings in a customized and efficient manner. It works by replacing characters that are preceded by your escape char (or phrase) There are two ways to call this module:
 
From another module:
 local esc = require('Module:Escape')
 esc:char({{green|''escape char (or sequence)''}})
 local to_escape = esc:text({{green|''string''}})
 {{green|''code that replaces or removes unescaped chars''}}
 local result = esc:undo(to_escape)
 
From a template:
 <nowiki>{{invoke:Escape|main|mode=</nowiki>{{green|''function''}}|char={{green|''escape char (or sequence)''}}|{{green|''text''}}}}
 
In a template, the most useful function is {{code|kill}}. 
 
 
This module is primarily intended to be used by other modules. However all functions can be called in template space using {{para|mode|the function you want to call}} followed by arguments.
 
All module functions (i.e. any func. other than main()) should be called using a colon (:), e.g. {{code|esc:char('%')}} or <code><nowiki>esc:kill{'{{example|\\}}}', '}'} == '{{example|}'</nowiki></code>
 
 
{|class='wikitable' style='background:#fff'
|-
!style='vertical-align:top;width:7em'|{{TOC tab|escape:text()}}
|This function takes only one argument: A string. All characters in this string which are preceded by the sequence set by escape:char() will be replaced with placeholders that can be converted back into that char by escape:undo()
|-
!style='vertical-align:top;width:5em'|{{TOC tab|escape:undo()}}
|Takes two arguments:
# The string that may contain placeholders set by escape:text()
# Optional, a char to be placed in front of any characters that have been de-escaped. (i.e. if you need to re-escape those string with a different char)
|-
!style='vertical-align:top;width:5em'|{{TOC tab|escape:kill()}}
|This is basically equivalent to calling string.gsub() on the string returned by escape:text() and feeding that result into escape:undo() in a single step. Takes three arguments:
# A string
# A sequence of characters to be removed from that string. (May use a string.gsub pattern)
# Optional, a char to be placed in front of any characters that have been de-escaped.
|- 
!style='vertical-align:top'|{{TOC tab|escape:char()}}
|This function's primary use is to initialize the patterns to scan a string for an escape/escaped sequence. It takes two arguments, the first being the escape character and the second being a table of arguments (optional). By default, this module will escape the {{code|\}} char. To escape the {{code|{}} char instead, you can do {{code|require('Module:Escape'):char('{')}} (or {{code|esc:char('{')}} (presuming you stored the table returned by this module in the local variable {{code|esc}}).
 
When called without the second argument, char() will return a table containing the functions. This allows, for example, <code>escape:char('*'):kill('1*23', '%d')</code> which would return '2'
 
For the most part, there is very little reason to set {{para|mode}} in template space since the patterns it stores are not shared with other invokations of this module. Templates should instead use the {{para|char}} if a new escape sequence is desired.
 
====Shortcut====
If provided a second argument that is a table containing a {key = value} pair, such that the key is {{code|text}}, {{code|undo}}, or {{code|kill}} and the value is a table containing the arguments that would have been passed to those functions. For escape:undo(), will cause the escaescape:text() and escape:kill()
 
 
|}
<span id='functions doc'></span>
 
===Caveats===
* When using a multi-character escape sequence, this module only marks it using the byte value of the first character. Thus, escape:undo() will unescape, for example, all characters escaped with 'e' and 'esc' if both were used. In practice however this shouldn't be a problem as multiple escape sequences are pretty rare unless you're transitioning between multiple code languages. (Multiple multi-char escape sequences beginning with the same character are simply bad practice anyhow.)
* Since byte values are stored as numbers, it is not recommended for you to use a number as an escape sequence (though it may work just fine).
* Placeholder byte values separated with return ('\r') characters--chosen because they are seldom used at all, and virtually never used unpaired with '\n'; moreover, it is distinct from the markers generated by {{tag|nowiki}} or {{code|mw.text.nowiki()}} (which use the delete char). To set a different separator char, include the key-value pair <code>{safeChr = {{green|alternate character}}}</code> in the table that you pass to escape:char().
 
==Speed==
The following are benchmarks...
 
when executing the following module function:
 function p.test_kill500(frame)
  local esc = require('Module:Escape')
  for k = 1, 500 do
   local v = esc:kill(p.test_string2(), 'test')
  end
  return os.clock(esc)
 end
'''{{#invoke:Escape/testcases|test_kill500}}'''
 
 
when repeating the following line 500 times in a template:
 
{{code|<nowiki>{{#invoke:Escape|main|mode=kill|{{#invoke:Escape/testcases|test_string2}}|test}}</nowiki>}}
 
'''0.767'''<!-- 
NewPP limit report
Parsed by mw1144
CPU time usage: 1.082 seconds
Real time usage: 1.109 seconds
Preprocessor visited node count: 4001/1000000
Preprocessor generated node count: 0/1500000
Post‐expand include size: 33000/2097152 bytes
Template argument size: 0/2097152 bytes
Highest expansion depth: 3/40
Expensive parser function count: 0/500
Lua time usage: 0.767/10.000 seconds
Lua memory usage: 1.5 MB/50 MB
-->
 
All times in seconds. The module time x500 was calculated when you loaded this doc page (normally between 0.02 and 0.07). The template time x500 was recorded on Jan 15, 2015.
 
==Examples==
===Template===
{{Module talk:Escape/testcases}}
===Module===
Here's some sample output from the debug consol below the module editor:
{|- class='wikitable'
|
{{blue|'''local escape {{=}} require('Module:Escape')<br>test {{=}} '{{#invoke:Escape/testcases|test_string_module}}'<br><br>test2 {{=}} escape:char('{'):text(test)<br>{{=}}test2'''}}<br>
{{#invoke:Escape|main
|mode=text
|char={
|{{#invoke:Escape/testcases|test_string}}
}}
 
{{blue|'''test3 {{=}} escape:char('\\'):text(test2)<br>{{=}}test3'''}}<br>
{{#invoke:Escape|main
|mode=text
|{{#invoke:Escape|main
 |mode=text
 |char={
 |{{#invoke:Escape/testcases|test_string}}
 }}
}}
 
{{blue|'''test4 {{=}} escape:char('{', {undo {{=}} test3})<br>{{=}}test4'''}}<br>
{{#invoke:Escape|main|mode=undo
|char={
|{{#invoke:Escape|main|mode=text
 |{{#invoke:Escape|main|mode=text
  |char={
  |{{#invoke:Escape/testcases|test_string}}
  }}
 }}
}}
 
{{blue|'''test4 {{=}} escape:char('\\', {undo {{=}} test3})<br>{{=}}test4'''}}<br>
{{#invoke:Escape|main
|mode=undo
|{{#invoke:Escape|main
 |mode=text
 |{{#invoke:Escape|main
  |mode=text
  |char={
  |{{#invoke:Escape/testcases|test_string}}}}
 }}
}}
 
{{blue|'''test5 {{=}} escape:char('{', {undo {{=}} test4})<br>{{=}}test5 {{=}}{{=}} test'''}}<br>
{{#ifeq:
 {{#invoke:Escape|main
 |mode=undo
 |char={
 |{{#invoke:Escape|main
  |mode=undo
  |{{#invoke:Escape|main
   |mode=text
   |{{#invoke:Escape|main
    |mode=text
    |char={
    |{{#invoke:Escape/testcases|test_string}}
    }}
   }}|\
  }}|{
 }}
|{{#invoke:Escape/testcases|test_string}}
|true
|false
}}
 
'''{{blue|{{=}}escape:undo(test3)}}'''{{green|--doesn't work because char is still set to '{' in current session}}<br>
<!--Obviously template calls don't remember sessions so we must code it here-->
{{#invoke:Escape|main|mode=undo
|char={
|{{#invoke:Escape|main|mode=text|{{#invoke:Escape|main|mode=text|char={|{{#invoke:Escape/testcases|test_string}}}}}}
}}
 
'''{{blue|{{=}}escape:undo(test4)}}<br>
{{#invoke:Escape|main|mode=undo
|char={
|{{#invoke:Escape|main|mode=undo
 |{{#invoke:Escape|main|mode=text
  |{{#invoke:Escape|main|mode=text
   |char={
   |{{#invoke:Escape/testcases|test_string}}
  }}
 }}
 |\}}
}}
 
'''{{blue|{{=}}escape:char('\\'):undo(test3)}}<br>
{{#invoke:Escape|main
|mode=undo
|{{#invoke:Escape|main|mode=text|{{#invoke:Escape|main|mode=text|char={|{{#invoke:Escape/testcases|test_string}}}}}}
}}
 
'''{{blue|{{=}}escape:char('{', {undo {{=}} escape:char('\\'):undo(test3)})}}<br>
{{#invoke:Escape|main|mode=undo|char={
|{{#invoke:Escape|main|mode=undo|{{#invoke:Escape|main|mode=text|{{#invoke:Escape|main|mode=text|char={|{{#invoke:Escape/testcases|test_string}}}}}}}}
|{
}}
 
'''{{blue|{{=}}test {{=}}{{=}} escape:char('{', {undo {{=}} escape:char('\\'):undo(test3)})}}<br>
false
 
'''{{blue|{{=}}test {{=}}{{=}} escape:char('{', {undo {{=}} escape:char('\\'):undo(test3, '\\')})}}<br>
{{#ifeq:
{{#invoke:Escape|main
|mode=char
|char={
|undo={{#invoke:Escape|main
 |mode=char
 |char=\
 |undo={{#invoke:Escape|main|mode=text|{{#invoke:Escape|main|mode=text|char={|{{#invoke:Escape/testcases|test_string}}}}}}
 }}
}}
|{{#invoke:Escape/testcases|test_string}}
|true
|false
}}
 
'''{{blue|local t {{=}} '{{#invoke:Escape/testcases|test_string_module|2}}'<br>{{=}}t}}<br>'''
{{#invoke:Escape/testcases|test_string2}}
 
'''{{blue|local e {{=}} require('Module:Escape')<br>local t2 {{=}} escape:text(t)<br>local t3 {{=}} string.gsub(t2, '{', '')<br>local t4 {{=}} escape:undo(t3)<br>{{=}}t4}}<br>'''
test  test { test, test, {,test   \
 
'''{{blue|local tk0 {{=}} escape:kill(t, '{')<br>{{=}}tk0 {{=}}{{=}} t4}}<br>'''
true
 
|}
<includeonly>{{#ifeq:{{SUBPAGENAME}}|sandbox | |
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}}</includeonly>

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