![]() | Chapter 19: Advanced Text | ![]() ![]() |
19.8. Replacements |
Suppose V is an indexed text which varies - perhaps a property of something, or a variable defined everywhere, or a temporary "let"-named value. How do we change its contents? The easiest way is simply to assign text to it. Thus:
let V be "It is now [the time of the day in words]."
And, for instance,
let V be "[V]!"
adds an exclamation mark at the end of V.
Otherwise, it is more useful (also a little faster) to modify V by changing its characters, words and so on. Thus:
replace character number N in V with NEW
changes the Nth character to NEW (which is not required to be a single character: it simply occupies the spot previously occupied by the Nth character). Similarly:
replace word number N in V with NEW
replace punctuated word number N in V with NEW
replace unpunctuated word number N in V with NEW
replace line number N in V with NEW
replace paragraph number N in V with NEW
Last, but not least, we can replace text wherever it occurs:
replace the text FIND in V with NEW
replace the text FIND in V with NEW, case insensitively
replace the regular expression FIND in V with NEW
replace the regular expression FIND in V with NEW, case insensitively
These match as much as they can, but again, with the matches not allowed to overlap. Thus
replace the text "a" in V with "z"
changes every lower-case "a" to "z": the same thing done case insensitively would change each "a" or "A" to "z".
When replacing a regular expression, the replacement text also has a few special meanings (though, thankfully, many fewer than for the expression itself). Once again "\n" and "\t" can be used for line break and tab characters, and "\\" must be used for an actual backslash. But, very usefully, "\1" to "\9" expand as the contents of groups numbered 1 to 9, and "\0" to the exact text matched. So:
replace the regular expression "\d+" in V with "roughly \0"
adds the word "roughly" in front of any run of digits in V, because \0 becomes in turn whichever run of digits matched. And
replace the regular expression "(\w+) (.*)" in V with "\2, \1"
performs the transformation "Frank Booth" to "Booth, Frank".
Finally, prefixing the number by "l" or "u" forces the text it represents into lower or upper case, respectively. For instance:
replace the regular expression "\b(\w)(\w*)" in X with "\u1\l2";
changes the casing of X to "title casing", where each individual word is capitalised. (This is a little slow on large texts, since so many matches and replacements are made: it's more efficient to use the official phrases for changing case.)
| ![]() A dog the player can name and un-name at will. |
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| ![]() A pig Latin filter for the player's commands. |
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| ![]() Filtering the names of rooms printed while in darkness. |
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| ![]() ![]() Letting the player guess types for an unidentifiable fish. |
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| ![]() ![]() Making Inform understand ASK JOSH TO TAKE INVENTORY as JOSH, TAKE INVENTORY. This requires us to use a regular expression on the player's command, replacing some of the content. |
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