procedure

( wrap-expr/c contract-expr

expr

[ #:arg?arg?

#:positivepos-blame

#:negativeneg-blame

#:nameexpr-name

#:macromacro-name

#:contextcontext

#:phasephase]) → syntax?

contract-expr:syntax?

expr:syntax?

arg?:any/c =#t

pos-blame :

(or/c syntax? string? module-path-index?

'from-macro'use-site'unknown)

= 'from-macro

neg-blame :

(or/c syntax? string? module-path-index?

'from-macro'use-site'unknown)

= 'use-site

expr-name:(or/c identifier? symbol? string? #f)=#f

macro-name:(or/c identifier? symbol? string? #f)=#f

context:(or/c syntax? #f)=(current-syntax-context )

phase:exact-integer? =(syntax-local-phase-level )

> (define-syntax (myparameterize1stx)

(syntax-case stx()

[(_ ([pv])body)

(with-syntax ([cp(wrap-expr/c

#'parameter? #'p

#:name"the parameter argument"

#:contextstx)])

#'(parameterize ([cpv])body))]))

> (myparameterize1([current-input-port

(open-input-string "(1 2 3)")])

(read ))

'(1 2 3)

> (myparameterize1(['whoops'something])

'whatever)

myparameterize1: contract violation

expected: parameter?

given: 'whoops

in: parameter?

macro argument contract on the parameter argument

contract from: top-level

blaming: top-level

(assuming the contract is correct)

at: eval:4:0

> (module modracket

(require (for-syntax syntax/contract))

(define-syntax (appstx)

(syntax-case stx()

[(appfarg)

(with-syntax ([cf(wrap-expr/c

#'(-> number? number? )

#'f

#:name"the function argument"

#:contextstx)])

#'(cfarg))]))

(provide app))

> (require 'mod)

> (appadd1 5)

6

> (appadd1 'apple)

app: broke its own contract

promised: number?

produced: 'apple

in: the 1st argument of

(-> number? number?)

macro argument contract on the function argument

contract from: 'mod

blaming: (quote mod)

(assuming the contract is correct)

at: eval:8:0

> (app(lambda (x)'pear)5)

app: contract violation

expected: number?

given: 'pear

in: the range of

(-> number? number?)

macro argument contract on the function argument

contract from: 'mod

blaming: top-level

(assuming the contract is correct)

at: eval:9:0