retroforth/doc/html/chapters/techniques/strings.html

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<p><span class="h1">Working With Strings</span>
<br/><br/>
Strings in RETRO are NULL terminated sequences of values
representing characters. Being NULL terminated, they can't
contain a NULL (ASCII 0).
<br/><br/>
The character words in RETRO are built around ASCII, but
strings can contain UTF8 encoded data if the host platform
allows. Words like <span class="tt">s:length</span> will return the number of bytes,
not the number of logical characters in this case.
<br/><br/>
<span class="h2">Prefix</span>
<br/><br/>
Strings begin with a single <span class="tt">'</span>.
<br/><br/>
<tt class='indentedcode'>'Hello</tt>
<tt class='indentedcode'>'This_is_a_string</tt>
<tt class='indentedcode'>'This_is_a_much_longer_string_12345_67890_!!!</tt>
<br/><br/>
RETRO will replace spaces with underscores. If you need both
spaces and underscores in a string, escape the underscores and
use <span class="tt">s:format</span>:
<br/><br/>
<tt class='indentedcode'>'This_has_spaces_and_under\_scored_words.&nbsp;s:format</tt>
<br/><br/>
<span class="h2">Namespace</span>
<br/><br/>
Words operating on strings are in the <span class="tt">s:</span> namespace.
<br/><br/>
<span class="h2">Lifetime</span>
<br/><br/>
At the interpreter, strings get allocated in a rotating buffer.
This is used by the words operating on strings, so if you need
to keep them around, use <span class="tt">s:keep</span> or <span class="tt">s:copy</span> to move them to
more permanent storage.
<br/><br/>
In a definition, the string is compiled inline and so is in
permanent memory.
<br/><br/>
You can manually manage the string lifetime by using <span class="tt">s:keep</span>
to place it into permanent memory or <span class="tt">s:temp</span> to copy it to
the rotating buffer.
<br/><br/>
<span class="h2">Mutability</span>
<br/><br/>
Strings are mutable. If you need to ensure that a string is
not altered, make a copy before operating on it or see the
individual glossary entries for notes on words that may do
this automatically.
<br/><br/>
<span class="h2">Searching</span>
<br/><br/>
RETRO provides four words for searching within a string.
<br/><br/>
&bull; <span class="tt">s:contains-char?</span> <br/>
&bull; <span class="tt">s:contains-string?</span><br/>
&bull; <span class="tt">s:index-of</span><br/>
&bull; <span class="tt">s:index-of-string</span><br/>
<br/><br/>
<span class="h2">Comparisons</span>
<br/><br/>
&bull; <span class="tt">s:eq?</span><br/>
&bull; <span class="tt">s:case</span><br/>
<br/><br/>
<span class="h2">Extraction</span>
<br/><br/>
To obtain a new string containing the first <span class="tt">n</span> characters from
a source string, use <span class="tt">s:left</span>:
<br/><br/>
<tt class='indentedcode'>'Hello_World&nbsp;#5&nbsp;s:left</tt>
<br/><br/>
To obtain a new string containing the last <span class="tt">n</span> characters from
a source string, use <span class="tt">s:right</span>:
<br/><br/>
<tt class='indentedcode'>'Hello_World&nbsp;#5&nbsp;s:right</tt>
<br/><br/>
If you need to extract data from the middle of the string, use
<span class="tt">s:substr</span>. This takes a string, the offset of the first
character, and the number of characters to extract.
<br/><br/>
<tt class='indentedcode'>'Hello_World&nbsp;#3&nbsp;#5&nbsp;s:substr</tt>
<br/><br/>
<span class="h2">Joining</span>
<br/><br/>
You can use <span class="tt">s:append</span> or <span class="tt">s:prepend</span> to merge two strings.
<br/><br/>
<tt class='indentedcode'>'First&nbsp;'Second&nbsp;s:append</tt>
<tt class='indentedcode'>'Second&nbsp;'First&nbsp;s:prepend</tt>
<br/><br/>
<span class="h2">Tokenization</span>
<br/><br/>
&bull; <span class="tt">s:tokenize</span><br/>
&bull; <span class="tt">s:tokenize-on-string</span><br/>
&bull; <span class="tt">s:split</span><br/>
&bull; <span class="tt">s:split-on-string</span><br/>
<br/><br/>
<span class="h2">Conversions</span>
<br/><br/>
To convert the case of a string, RETRO provides <span class="tt">s:to-lower</span>
and <span class="tt">s:to-upper</span>.
<br/><br/>
<span class="tt">s:to-number</span> is provided to convert a string to an integer
value. This has a few limitations:
<br/><br/>
&bull; only supports decimal<br/>
&bull; non-numeric characters will result in incorrect values<br/>
<br/><br/>
<span class="h2">Cleanup</span>
<br/><br/>
RETRO provides a handful of words for cleaning up strings.
<br/><br/>
<span class="tt">s:chop</span> will remove the last character from a string. This
is done by replacing it with an ASCII:NULL.
<br/><br/>
<span class="tt">s:trim</span> removes leading and trailing whitespace from a string.
For more control, there is also <span class="tt">s:trim-left</span> and <span class="tt">s:trim-right</span>
which let you trim just the leading or trailing end as desired.
<br/><br/>
<span class="h2">Combinators</span>
<br/><br/>
&bull; <span class="tt">s:for-each</span><br/>
&bull; <span class="tt">s:filter</span><br/>
&bull; <span class="tt">s:map</span><br/>
<br/><br/>
<span class="h2">Other</span>
<br/><br/>
&bull; <span class="tt">s:evaluate</span><br/>
&bull; <span class="tt">s:copy</span><br/>
&bull; <span class="tt">s:reverse</span><br/>
&bull; <span class="tt">s:hash</span><br/>
&bull; <span class="tt">s:length</span><br/>
&bull; <span class="tt">s:replace</span><br/>
&bull; <span class="tt">s:format</span><br/>
&bull; <span class="tt">s:empty</span><br/>
<br/><br/>
<span class="h2">Controlling The Temporary Buffers</span>
<br/><br/>
As dicussed in the Lifetime subsection, temporary strings are
allocated in a rotating buffer. The details of this can be
altered by updating two variables.
<br/><br/>
<tt class='indentedcode'>|&nbsp;Variable&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;Holds&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|</tt>
<tt class='indentedcode'>|&nbsp;-------------&nbsp;|&nbsp;----------------------------------------&nbsp;|</tt>
<tt class='indentedcode'>|&nbsp;TempStrings&nbsp;&nbsp;&nbsp;|&nbsp;The&nbsp;number&nbsp;of&nbsp;temporary&nbsp;strings&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|</tt>
<tt class='indentedcode'>|&nbsp;TempStringMax&nbsp;|&nbsp;The&nbsp;maximum&nbsp;length&nbsp;of&nbsp;a&nbsp;temporary&nbsp;string&nbsp;|</tt>
<br/><br/>
For example, to increase the number of temporary strings to
48:
<br/><br/>
<tt class='indentedcode'>#48&nbsp;!TempStrings</tt>
<br/><br/>
The defaults are:
<br/><br/>
<tt class='indentedcode'>|&nbsp;Variable&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;Default&nbsp;|</tt>
<tt class='indentedcode'>|&nbsp;-------------&nbsp;|&nbsp;-------&nbsp;|</tt>
<tt class='indentedcode'>|&nbsp;TempStrings&nbsp;&nbsp;&nbsp;|&nbsp;32&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|</tt>
<tt class='indentedcode'>|&nbsp;TempStringMax&nbsp;|&nbsp;512&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|</tt>
<br/><br/>
It's also important to note that altering these will affect
the memory map for all temporary buffers. Do not use anything
already in the buffers after updating these or you will risk
data corruption and possible crashes.
</p>
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