Walnut/Advanced Topics/Build your Own Guards - Revision history

ThomasLeonard: Simple guard example

2010-01-26T11:23:09Z

Simple guard example

New page

[[Category:Walnut|7]]

===Build Your Own Guards===

<code># E template
def simple_guard {
to coerce(specimen, optEjector) :near {
if (specimen fits criteria) {
return specimen
} else {
throw.eject(optEjector, "Specimen didnt fit criteria")
}
}
}
</code>

First, here is a simple guard that matches integer strings and converts them to integers:

def asInt {
to coerce(specimen, optEjector) :int {
try {
return __makeInt(specimen :String)
} catch ex {
throw.eject(optEjector, ex)
}
}
}

You can use it like this:

def str := "5 + 7 = 12"
def `@{a:asInt} + @{b:asInt} = @{c:asInt}` := str
require(a + b == c)

Now for a more complicated example...

Here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):

<code># E sample
def makeVOCPair(brandName :String) :near {

var myTempContents := def none {}

def brand {
to __printOn(out :TextWriter) :void {
out.print(brandName)
}
}

def ProveAuth {
to __printOn(out :TextWriter) :void {
out.print(`<$brandName prover>`)
}
to getBrand() :near { return brand }
to coerce(specimen, optEjector) :near {
def sealedBox {
to getBrand() :near { return brand }
to offerContent() :void {
myTempContents := specimen
}
}
return sealedBox
}
}
def CheckAuth {
to __printOn(out :TextWriter) :void {
out.print(`<$brandName checker template>`)
}
to getBrand() :near { return brand }
match [`get`, authList :any[]] {
def checker {
to __printOn(out :TextWriter) :void {
out.print(`<$brandName checker>`)
}
to getBrand() :near { return brand }
to coerce(specimenBox, optEjector) :any {
myTempContents := null
if (specimenBox.__respondsTo("offerContent", 0)) {
<font color="#FF0000"># XXX Using __respondsTo/2 here is a kludge</font>
specimenBox.offerContent()
} else {
myTempContents := specimenBox
}
for auth in authList {
if (auth == myTempContents) {
return auth
}
}
myTempContents := none
throw.eject(optEjector,
`Unmatched $brandName authorization`)
}
}
}
match [`__respondsTo`, [`get`, _]] {
true
}
match [`__respondsTo`, [_, _]] {
false
}
match [`__getAllegedType`, []] {
null.__getAllegedType()
}
}
return [ProveAuth, CheckAuth]
}</code>

Now here is an example of the pair of VOC guards in use:

<pre>? def [ProveAuth, CheckAuth] := <elib:sealing.makeVOCPair>("voc")
# value: [<voc prover>, <voc checker template>]

? def f1 := <file:~/.bashrc>
# value: <file:c:/Documents and Settings/millerm1/.bashrc>

? def f2 := <file:~/Desktop>
# value: <file:c:/Documents and Settings/millerm1/Desktop/>

? def foo(f :CheckAuth[f1,f2]) :void {
> println(f.getPath())
> }
# value: <foo>

? foo(f1)
# stdout: c:/Documents and Settings/millerm1/.bashrc
#

? def f3 := <file:~>
# value: <file:c:/Documents and Settings/millerm1/>

? foo(f3)
# problem: Unmatched voc authorization

? foo(f1 :ProveAuth)
# stdout: c:/Documents and Settings/millerm1/.bashrc
#

? foo(f3 :ProveAuth)
# problem: Unmatched voc authorization

? def bar(f) :void {
> println(f.getPath())
> }
# value: <bar>

? bar(f1)
# stdout: c:/Documents and Settings/millerm1/.bashrc
#

? bar(f1 :ProveAuth)
# problem: <NoSuchMethodException: <a sealedBox>.getPath/0></pre>

Zarutian: /* Build Your Own Guards */

2008-01-17T04:58:32Z

Build Your Own Guards

←Older revision		Revision as of 04:58, 17 January 2008
Line 4:		Line 4:

	<span style="color:red">Put in explanation of the following example. First put in a simple example. This is way too fancy as the basic intro to making a guard.</span>		<span style="color:red">Put in explanation of the following example. First put in a simple example. This is way too fancy as the basic intro to making a guard.</span>
		+
		+	<code># E template
		+	def simple_guard {
		+	to coerce(specimen, optEjector) :near {
		+	if (specimen fits criteria) {
		+	return specimen
		+	} else {
		+	throw.eject(optEjector, "Specimen didnt fit criteria")
		+	}
		+	}
		+	}
		+	</code>

	First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):		First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):

217.81.31.185: /* Build Your Own Guards */

2006-12-06T11:00:36Z

Build Your Own Guards

←Older revision		Revision as of 11:00, 6 December 2006
Line 7:		Line 7:
	First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):		First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):

-	<~~pre~~># E sample	+	<code># E sample
	def makeVOCPair(brandName :String) :near {		def makeVOCPair(brandName :String) :near {

Line 74:		Line 74:
	}		}
	return [ProveAuth, CheckAuth]		return [ProveAuth, CheckAuth]
-	}</~~pre~~>	+	}</code>

	Now here is an example of the pair of VOC guards in use:		Now here is an example of the pair of VOC guards in use:

217.81.31.185: /* Build Your Own Guards */

2006-12-06T11:00:06Z

Build Your Own Guards

←Older revision		Revision as of 11:00, 6 December 2006
Line 7:		Line 7:
	First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):		First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):

-	<~~code~~># E sample	+	<pre># E sample
	def makeVOCPair(brandName :String) :near {		def makeVOCPair(brandName :String) :near {

Line 74:		Line 74:
	}		}
	return [ProveAuth, CheckAuth]		return [ProveAuth, CheckAuth]
-	}</~~code~~>	+	}</pre>

	Now here is an example of the pair of VOC guards in use:		Now here is an example of the pair of VOC guards in use:

217.81.31.185: /* Build Your Own Guards */

2006-12-06T10:59:24Z

Build Your Own Guards

←Older revision		Revision as of 10:59, 6 December 2006
Line 47:		Line 47:
	myTempContents := null		myTempContents := null
	if (specimenBox.__respondsTo("offerContent", 0)) {		if (specimenBox.__respondsTo("offerContent", 0)) {
-	<font color=#FF0000># XXX Using __respondsTo/2 here is a kludge</font>	+	<font color="#FF0000"># XXX Using __respondsTo/2 here is a kludge</font>
	specimenBox.offerContent()		specimenBox.offerContent()
	} else {		} else {

217.81.31.185: /* Build Your Own Guards */

2006-12-06T10:58:27Z

Build Your Own Guards

←Older revision		Revision as of 10:58, 6 December 2006
Line 47:		Line 47:
	myTempContents := null		myTempContents := null
	if (specimenBox.__respondsTo("offerContent", 0)) {		if (specimenBox.__respondsTo("offerContent", 0)) {
-	<~~nowiki><span style~~=~~"color:~~#FF0000;"># XXX Using __respondsTo/2 here is a kludge</~~span></nowiki~~>	+	<font color=#FF0000># XXX Using __respondsTo/2 here is a kludge</font>
	specimenBox.offerContent()		specimenBox.offerContent()
	} else {		} else {

217.81.31.185: /* Build Your Own Guards */

2006-12-06T10:56:50Z

Build Your Own Guards

←Older revision		Revision as of 10:56, 6 December 2006
Line 7:		Line 7:
	First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):		First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):

-	<~~pre~~># E sample	+	<code># E sample
	def makeVOCPair(brandName :String) :near {		def makeVOCPair(brandName :String) :near {

Line 74:		Line 74:
	}		}
	return [ProveAuth, CheckAuth]		return [ProveAuth, CheckAuth]
-	}</~~pre~~>	+	}</code>

	Now here is an example of the pair of VOC guards in use:		Now here is an example of the pair of VOC guards in use:

217.81.31.185: /* Build Your Own Guards */

2006-12-06T10:51:54Z

Build Your Own Guards

←Older revision		Revision as of 10:51, 6 December 2006
Line 47:		Line 47:
	myTempContents := null		myTempContents := null
	if (specimenBox.__respondsTo("offerContent", 0)) {		if (specimenBox.__respondsTo("offerContent", 0)) {
-	<span style="color:#FF0000;"># XXX Using __respondsTo/2 here is a kludge</span>	+	<nowiki><span style="color:#FF0000;"># XXX Using __respondsTo/2 here is a kludge</span></nowiki>
	specimenBox.offerContent()		specimenBox.offerContent()
	} else {		} else {

217.81.31.185: /* Build Your Own Guards */

2006-12-06T10:50:26Z

Build Your Own Guards

←Older revision		Revision as of 10:50, 6 December 2006
Line 47:		Line 47:
	myTempContents := null		myTempContents := null
	if (specimenBox.__respondsTo("offerContent", 0)) {		if (specimenBox.__respondsTo("offerContent", 0)) {
-	<~~font color~~="#FF0000"># XXX Using __respondsTo/2 here is a kludge</~~font~~>	+	<span style="color:#FF0000;"># XXX Using __respondsTo/2 here is a kludge</span>
	specimenBox.offerContent()		specimenBox.offerContent()
	} else {		} else {

Mscheffler: /* Build Your Own Guards */

2006-12-06T10:49:19Z

Build Your Own Guards

←Older revision		Revision as of 10:49, 6 December 2006
Line 7:		Line 7:
	First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):		First, here is the emaker that makes a pair of VOC claim check guards, a proveAuth (i.e., a claimCheck), and a checkAuth (i.e., a checkedClaim):

-	<pre>	+	<pre># E sample
-		+
-	~~<nowiki~~># E sample	+
	def makeVOCPair(brandName :String) :near {		def makeVOCPair(brandName :String) :near {

Line 49:		Line 47:
	myTempContents := null		myTempContents := null
	if (specimenBox.__respondsTo("offerContent", 0)) {		if (specimenBox.__respondsTo("offerContent", 0)) {
-	~~</nowiki>~~<font color="#FF0000"~~><nowiki~~># XXX Using __respondsTo/2 here is a kludge~~</nowiki>~~</font>	+	<font color="#FF0000"># XXX Using __respondsTo/2 here is a kludge</font>
	specimenBox.offerContent()		specimenBox.offerContent()
	} else {		} else {
Line 76:		Line 74:
	}		}
	return [ProveAuth, CheckAuth]		return [ProveAuth, CheckAuth]
-	}	+	}</pre>
-		+
-	</pre>	+

	Now here is an example of the pair of VOC guards in use:		Now here is an example of the pair of VOC guards in use:

-	<pre>	+	<pre>? def [ProveAuth, CheckAuth] := <elib:sealing.makeVOCPair>("voc")
-		+
-	? def [ProveAuth, CheckAuth] := <elib:sealing.makeVOCPair>("voc")	+
	# value: [<voc prover>, <voc checker template>]		# value: [<voc prover>, <voc checker template>]

Line 125:		Line 119:

	? bar(f1 :ProveAuth)		? bar(f1 :ProveAuth)
-	# problem: <NoSuchMethodException: <a sealedBox>.getPath/0>	+	# problem: <NoSuchMethodException: <a sealedBox>.getPath/0></pre>
-		+
-		+
-	</pre>	+