# Syntax Utilities

Utilities for expanders.

(import (for-syntax :std/stxutil))

# format-id

(format-id ctx fmt arg ...) -> identifier

  ctx := context identifier
  fmt := a format string, as in :std/format
  arg := a format argument; syntax objects are automatically unwrapped

Formats an identifier, using fmt as the format string and ctx as the syntactic context.

(import (for-syntax :std/stxutil))
(defsyntax (make-pred stx)
  (syntax-case stx ()
    ((_ id) (format-id #'id "~a?" #'id))))

> (make-pred pair)
=> #<procedure #8 pair?>

# maybe-make-symbol

(maybe-make-symbol str str+ ...) -> symbol-or-string

Concatenates string designators str str+ into a string as by as-string, and either returns a thus-named interned symbol if it already interned, or returns a string if no such symbol was interned.

This is useful when reading data from not-fully-trusted sources, that you want to match against existing symbol infrastructure, but should not be allowed to intern spamfuls of symbols into your memory to make it leak away and trigger more errors.

> (maybe-make-symbol 'symbol '- 'not "-interned-yet")
"symbol-not-interned-yet"

> (maybe-make-symbol "sym" "bol")
symbol

# maybe-make-keyword

(maybe-make-keyword str str+ ...) -> keyword-or-string

Concatenates string designators str str+ into a string as by as-string, and either returns a thus-named interned keyword if it already interned, or returns a string if no such keyword was interned.

This is useful when reading data from not-fully-trusted sources, that you want to match against existing keyword infrastructure, but should not be allowed to intern spamfuls of keywords into your memory to make it leak away and trigger more errors.

> (maybe-make-keyword 'keyword '- 'not "-interned-yet")
"keyword-not-interned-yet"

> (maybe-make-keyword "key" "word")
keyword: