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![def binarySearch(
a: Array[Int], left: Int, right: Int, x: Int
): Int = {
require(left >= 0 && right < a.length)
if(left > right) -1 else {
val m = (left + right)/2
val element = a(m)
if(x < element) {
binarySearch(a, left, m-1, x)
} else if(x > element) {
binarySearch(a, m+1, right, x)
} else {
m
}
}
}](https://image.slidesharecdn.com/scala-matsuri-slides-170808082945/85/Safety-Beyond-Types-3-320.jpg)
![def binarySearch(
a: Array[Int], left: Int, right: Int, x: Int
): Int = {
require(left >= 0 && right < a.length)
if(left > right) -1 else {
val m = (left + right)/2
//assert(m >= 0 && m < a.length)
val element = a(m)
if(x < element) {
//assert(left >= 0 && m-1 < a.length)
binarySearch(a, left, m-1, x)
} else if(x > element) {
//assert(m+1 >= 0 && right < a.length)
binarySearch(a, m+1, right, x)
} else {
m
}
}
}](https://image.slidesharecdn.com/scala-matsuri-slides-170808082945/85/Safety-Beyond-Types-4-320.jpg)
Uploaded byscalaconfjp
Safety Beyond Types
The document discusses the Leon Verification System, an open source tool that can statically analyze Scala code to prove the absence of certain errors. It verifies code by checking assertions and function contracts without running the code. Leon can also synthesize valid code from specifications, check for code termination, and perform automated program repair. The document demonstrates Leon's capabilities on a binary search algorithm example and notes some of Leon's main limitations, such as support for object-oriented features. It provides information on how to access and use Leon online or via GitHub.
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Safety Beyond Types
- 1. Safety Beyond Types WritingCorrect Software with Leon Régis Blanc @regbla EPFL, LARA 型を超えた安全 - Leon で正しいソフトウェアを書く
- 2. The Leon VerificationSystem ● Verifier for a subset of Scala ● Analyzes code statically – If issue detected: display an example that can trigger the problem – Otherwise, proves the absence of certain errors ● Open source project, developed at EPFL – Main contributions from LARA group 静的コード解析を行いコードの正しさを証明する
- 3. def binarySearch( a: Array[Int],left: Int, right: Int, x: Int ): Int = { require(left >= 0 && right < a.length) if(left > right) -1 else { val m = (left + right)/2 val element = a(m) if(x < element) { binarySearch(a, left, m-1, x) } else if(x > element) { binarySearch(a, m+1, right, x) } else { m } } }
- 4. def binarySearch( a: Array[Int],left: Int, right: Int, x: Int ): Int = { require(left >= 0 && right < a.length) if(left > right) -1 else { val m = (left + right)/2 //assert(m >= 0 && m < a.length) val element = a(m) if(x < element) { //assert(left >= 0 && m-1 < a.length) binarySearch(a, left, m-1, x) } else if(x > element) { //assert(m+1 >= 0 && right < a.length) binarySearch(a, m+1, right, x) } else { m } } }
- 5. Leon's Capabilities ● Staticverification of Scala code: – Validity of assertions – Ensure absence of some runtime errors – Ensure contract for each function ● Code synthesis Automatically generate valid code given some spec ● Termination checker ● Automated program repair Leon の機能 Scala コードの静的検証、コード合成、終了チェッカ、自動プログラム修復
- 6.
- 7. Main Limitations ● Object-orientedprogramming and subtyping ● Floating-point arithmetic ● Uniqueness constraint for mutable objects ● Custom standard library ● Verification is fundamentally undecidable
- 8. Get Leon ● Tryit online yourself: https://leon.epfl.ch/ ● Open source on GitHub: https://github.com/epfl-lara/leon ● Get in touch if you want to know more: – Email: regwblanc@gmail.com – Twitter: @regbla – GitHub: regb
- 9.