28 lines
858 B
Text
28 lines
858 B
Text
= zexps
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zexps, similar to g-expressions in Guix, are a way to generate
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S-expressions that are taggged with store paths. But that's where
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the similarity ends.
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To create a zexp, you can use either the full syntax, or the reader macro:
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[,scheme]
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----
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#~(foo bar #$baz)
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; is identical to:
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(zexp (foo bar (zexp-unquote baz)))
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----
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`(zexp-unquote VAL)` returns the value that the zexp (or any compatible record)
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contains, while gathering the `zexp-unquote`d values used.
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Like quasiquotation, zexps can use `unquote`, including ``zexp-unquote``d values
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inside the ``unquote``d code. ``unquote``d code is evaluated when the `zexp` is evaluated.
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[,scheme]
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----
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(define world #~,(begin (write "hello") "world"))
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(define hello #~("hello" ,(string-append "very " "cute") #$world))
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; When hello is used as zexp, it will also write "hello" to the output port.
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----
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