97 lines
4.8 KiB
HTML
97 lines
4.8 KiB
HTML
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<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head>
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<title>.</title>
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<style type="text/css">
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* { color: #000; background: #fff; max-width: 700px; }
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tt, pre { background: #dedede; color: #111; font-family: monospace;
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white-space: pre; display: block; width: 100%; }
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.indentedcode { margin-left: 2em; margin-right: 2em; }
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.codeblock {
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background: #dedede; color: #111; font-family: monospace;
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box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
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padding: 7px;
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display: block;
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}
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.indentedlist { margin-left: 2em; color: #000; }
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span { white-space: pre; }
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.text { color: #000; white-space: pre; background: #dedede; }
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.colon { color: #000; background: #dedede; }
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.note { color: #000; background: #dedede; }
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.str { color: #000; text-decoration: underline; background: #dedede; }
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.num { color: #000; background: #dedede; font-weight: bold; font-style: italic; }
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.fnum { color: #000; font-weight: bold; background: #dedede; }
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.ptr { color: #000; font-weight: bold; background: #dedede; }
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.fetch { color: #000; font-style: italic; background: #dedede; }
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.store { color: #000; font-style: italic; background: #dedede; }
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.char { color: #000; background: #dedede; }
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.inst { color: #000; background: #dedede; }
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.defer { color: #000; background: #dedede; }
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.imm { color: #000; font-weight: bold; background: #dedede; }
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.prim { color: #000; font-weight: bolder; background: #dedede; }
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.tt { white-space: pre; font-family: monospace; background: #dedede; }
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.h1, .h2, .h3, .h4 { white-space: normal; }
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.h1 { font-size: 125%; }
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.h2 { font-size: 120%; }
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.h3 { font-size: 115%; }
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.h4 { font-size: 110%; }
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.hr { display: block; height: 2px; background: #000000; }
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</style>
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</head><body>
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<p><span class="h3">On The Use Of Underscores In Word Names</span>
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<br/><br/>
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In brief: don't use underscores in word names.
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<br/><br/>
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There is a good reason for this, and it has to do with how RETRO
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processes strings. By default, underscores in strings are replaced
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by spaces. This is problematic when dealing with words like <span class="tt">var</span>,
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<span class="tt">const</span>, and <span class="tt">d:create</span> which take word names as strings.
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<br/><br/>
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Consider:
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<br/><br/>
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<tt class='indentedcode'>:hello_msg 'hello_user ;</tt>
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<tt class='indentedcode'>'test_name var</tt>
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<tt class='indentedcode'>#188 !test_name</tt>
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<br/><br/>
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In the first case, the <span class="tt">:</span> prefix handles the token, so the
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underscore is not remapped to a space, creating a word name as
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<span class="tt">hello_msg</span>. But in the second, the <span class="tt">'</span> prefix remaps the
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underscore to a space, giving a variable name of <span class="tt">test name</span>.
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In the third line, the name lookup will fail as <span class="tt">test_name</span> is
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not defined, so the store will be done to an incorrect address.
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<br/><br/>
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Because of this, it's best to avoid underscores in names.
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<br/><br/>
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Having covered this, if you do need to use them for some reason,
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you can replace <span class="tt">d:add-header</span> with a version that remaps spaces
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back to underscores before creating the header. The following
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will allow for this.
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<br/><br/>
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<tt class='indentedcode'>~~~</tt>
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<tt class='indentedcode'>{{</tt>
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<tt class='indentedcode'> :fields @Dictionary , (link) , (xt) , (class) ;</tt>
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<tt class='indentedcode'> :invalid-name? dup ASCII:SPACE s:contains-char? ;</tt>
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<tt class='indentedcode'> :rewrite [ ASCII:SPACE [ $_ ] case ] s:map ;</tt>
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<tt class='indentedcode'> :entry here &call dip !Dictionary ;</tt>
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<tt class='indentedcode'> [ [ fields invalid-name? &rewrite if s, (name) ] entry ]</tt>
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<tt class='indentedcode'>}}</tt>
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<br/><br/>
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<tt class='indentedcode'>#1793 &d:add-header store</tt>
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<tt class='indentedcode'>&d:add-header n:inc store</tt>
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<tt class='indentedcode'>~~~</tt>
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<br/><br/>
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Additional Note:
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<br/><br/>
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Some version of RETRO have included the above patch. The last
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release that will include this by default is 2020.4 as it is
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not needed by the majority of users. If you want to keep it in
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your system, you will need to load it yourself or add it to
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your <span class="tt">package/list.forth</span> (for Unix users) before building.
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</p>
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</body></html>
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