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Arc: Macros

Macros

Arc's macro system is more similar to Lisp than to Scheme; an Arc macro resembles a function that generates code.
Macros in Arc typically use quote and quasiquote to generate the code, and use uniq to generate unique symbols.
For details on the internals of Arc macros, see macro internals.
Macro mac name args [body ...]
Creates a macro.

>(mac mymac (a b) (+ a b)) #3(tagged mac #<procedure>)

Foundation macex macro
Expands a macro.

>(macex '(let a 1 (pr a))) ((fn (a) (pr a)) 1)

macex1 macro
Expands a macro to one level.

>(macex1 '(let a 1 (pr a))) (with (a 1) (pr a))

uniq
Generates a unique symbol.

>(uniq) gs2863

Macro w/uniq names [body ...]
Assigns a unique symbol to each name in names and executes body. names can either be a single symbol or a list of symbols.

>(w/uniq (a b c) (prn a b c)) gs2864gs2865gs2866 gs2864

Foundation quasiquote arg
The backquote ` is shorthand for quasiquote, e.g. `(+ 1 2) is the same as (quasiquote (1 2)). Inside quasiquote, the unquote operator will cause the contents to be evaluated instead of quoated. The unquote-splicing operator will cause contents to be evaluated and spliced into the result. , is shorthand for unquote, and ,@ is shorthand for unquote-splicing.

>`((+ 1 2) ,(+ 3 4) ,@(list 5 6)) ((+ 1 2) 7 5 6)

Foundation quote arg
The single quote ' is shorthand for quote, e.g. 'x is the same as (quote x)

>'(1 2 3) (1 2 3)

mac name args [body ...] Creates a macro.	>(mac mymac (a b) (+ a b)) #3(tagged mac #<procedure>)
macex macro Expands a macro.	>(macex '(let a 1 (pr a))) ((fn (a) (pr a)) 1)
macex1 macro Expands a macro to one level.	>(macex1 '(let a 1 (pr a))) (with (a 1) (pr a))
uniq Generates a unique symbol.	>(uniq) gs2863
w/uniq names [body ...] Assigns a unique symbol to each name in `names` and executes `body`. `names` can either be a single symbol or a list of symbols.	>(w/uniq (a b c) (prn a b c)) gs2864gs2865gs2866 gs2864
quasiquote arg The backquote ` is shorthand for `quasiquote`, e.g. `(+ 1 2) is the same as `(quasiquote (1 2))`. Inside `quasiquote`, the `unquote` operator will cause the contents to be evaluated instead of quoated. The `unquote-splicing` operator will cause contents to be evaluated and spliced into the result. `,` is shorthand for `unquote`, and `,@` is shorthand for `unquote-splicing`.	>`((+ 1 2) ,(+ 3 4) ,@(list 5 6)) ((+ 1 2) 7 5 6)
quote arg The single quote ' is shorthand for quote, e.g. 'x is the same as (quote x)	>'(1 2 3) (1 2 3)