at:tutorial:metaprogramming
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at:tutorial:metaprogramming [2007/07/27 07:21] – jdedecker | at:tutorial:metaprogramming [2008/08/01 14:31] – * tvcutsem | ||
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==== Quasiquoting and splicing ==== | ==== Quasiquoting and splicing ==== | ||
+ | Quasiquoting and splicing are an advanced and powerful metaprogramming techniques that control the evaluation process and allow one to manipulate the evaluation process of the abstract syntax tree. | ||
- | === Qouting | + | === Quoting |
Any valid AmbientTalk expression can be quoted. This prevents the expression from being evaluated. Instead, it is returned literally. | Any valid AmbientTalk expression can be quoted. This prevents the expression from being evaluated. Instead, it is returned literally. | ||
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</ | </ | ||
- | Note that in '' | + | Note that in '' |
== Expressions == | == Expressions == | ||
- | To quote a complete expression, it has to be wrapped in parantheses: | + | To quote a complete expression, it has to be wrapped in parentheses: |
< | < | ||
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== Statements == | == Statements == | ||
- | Statements (definitions, | + | Statements (definitions, |
< | < | ||
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With this construct, all the elements of the literal table are evaluated. By quoting a literal table, all the elements are quoted instead of evaluated: | With this construct, all the elements of the literal table are evaluated. By quoting a literal table, all the elements are quoted instead of evaluated: | ||
< | < | ||
- | > | + | > |
>> | >> | ||
</ | </ | ||
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>[ 7, 8, 9, @upTo(4) ] | >[ 7, 8, 9, @upTo(4) ] | ||
>>[7, 8, 9, 1, 2, 3, 4] | >>[7, 8, 9, 1, 2, 3, 4] | ||
+ | >[ 7, 8, 9, upTo(4) ] | ||
+ | >>[7, 8, 9, [1, 2, 3, 4]] | ||
</ | </ | ||
+ | In the example above the elements of the table returned by invoking **upTo(4)** are added in place to the table in which the expression was spliced. | ||
Splicing can also be used in combination with quoting and unquoting. AmbientTalk provides the // | Splicing can also be used in combination with quoting and unquoting. AmbientTalk provides the // | ||
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>read: " | >read: " | ||
>> | >> | ||
- | >eval: `(1+2) in: self | + | >def result := eval: `(1+2) in: self |
>>3 | >>3 | ||
- | > | + | > |
- | >>" | + | >>" |
</ | </ | ||
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< | < | ||
>def o := object: { def x := 4 } | >def o := object: { def x := 4 } | ||
- | >>< | + | >>< |
>eval: `x in: o | >eval: `x in: o | ||
>>4 | >>4 | ||
</ | </ |
at/tutorial/metaprogramming.txt · Last modified: 2009/11/21 07:44 by tvcutsem