new tasks

Task/Assertions/0DESCRIPTION

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+Assertions are a way of breaking out of code when there is an error or an unexpected input. Some languages throw [[exceptions]] and some treat it as a break point.
+
+Show an assertion in your language by asserting that an integer variable is equal to 42.

Task/Assertions/1META.yaml

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+---
+note: Basic language learning

Task/Assertions/C/assertions-2.c

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+assert(a == 42 && "Error message");

Task/Assertions/C/assertions.c

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+#include <assert.h>
+
+int main(){
+   int a;
+   /* ...input or change a here */
+   assert(a == 42); /* aborts program when a is not 42, unless the NDEBUG macro was defined */
+
+   return 0;
+}

Task/Assertions/Clojure/assertions.clj

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+(let [i 42]
+     (assert (= i 42)))

Task/Assertions/Eiffel/assertions-2.e

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+class TEST
+    feature assert(val: INTEGER) is
+        require
+            val = 42;
+        do
+            print("Thanks for the 42!%N");
+        end
+end

Task/Assertions/Eiffel/assertions.e

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+class MAIN
+    creation main
+    feature main is
+        local
+            test: TEST;
+        do
+            create test;
+
+            io.read_integer;
+            test.assert(io.last_integer);
+        end
+end

Task/Assertions/Erlang/assertions.erl

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+1> N = 42.
+42
+2> N = 43.
+** exception error: no match of right hand side value 43
+3> N = 42.
+42
+4> 44 = N.
+** exception error: no match of right hand side value 42
+5> 42 = N.
+42

Task/Assertions/Go/assertions.go

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+package main
+
+func main() {
+    x := 43
+    if x != 42 {
+        panic(42)
+    }
+}

Task/Assertions/Haskell/assertions.hs

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+import Control.Exception
+
+main = let a = someValue in
+         assert (a == 42) -- throws AssertionFailed when a is not 42
+                somethingElse -- what to return when a is 42

Task/Assertions/Java/assertions.java

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+public static void main(String[] args){
+   int a;
+   //...input or change a here
+   assert a == 42;//throws an AssertionError when a is not 42
+   assert a == 42 : "Error message"; //throws an AssertionError
+          //when a is not 42 with "Error message" for the message
+          //the error message can be any non-void expression
+}

Task/Assertions/Lua/assertions.lua

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+a = 5
+assert (a == 42)
+assert (a == 42,'\''..a..'\' is not the answer to life, the universe, and everything')

Task/Assertions/PHP/assertions.php

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+<?php
+$a = 5
+#...input or change $a here
+assert($a == 42) # when $a is not 42, take appropriate actions,
+                 # which is set by assert_options()
+?>

Task/Assertions/Perl/assertions-2.pl

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+use autodie;
+open my $fh, '<', 'file'; # automatically throws an exception on failure

Task/Assertions/Perl/assertions-3.pl

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+my $a = 5;
+#...input or change $a here
+$a == 42 or die "Error message\n";
+# or, alternatively:
+die "Error message\n" unless $a == 42;
+# or:
+die "Error message\n" if not $a == 42;
+# or just:
+die "Error message\n" if $a != 42;

Task/Assertions/Perl/assertions-4.pl

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+use Carp::Assert;
+assert($a == 42);

Task/Assertions/Perl/assertions-5.pl

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+is $a, 42;
+ok $a == 42;
+cmp_ok $a, '==', 42, 'The answer should be 42';
+# etc.

Task/Assertions/Perl/assertions.pl

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+open my $fh, '<', 'file' or die "Cannot open file: $!\n"; # $! contains the error message from the last error

Task/Assertions/PicoLisp/assertions-2.l

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+(let N 41
+   (unless (= N 42) (quit "Incorrect N" N)) )  # 'quit' throws an error
+41 -- Incorrect N
+?

Task/Assertions/PicoLisp/assertions-3.l

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+(let N 41
+   (unless (= N 42) (! setq N 42)) )   # '!' is a breakpoint
+(setq N 42)                            # Manually fix the value
+!                                      # Hit ENTER to leave the breakpoint
+-> 42

Task/Assertions/PicoLisp/assertions.l

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+...
+~(assert (= N 42))  # Exists only in debug mode
+...

Task/Assertions/Prolog/assertions.pro

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+test(A):-
+    assertion(A==42).

Task/Assertions/Python/assertions.py

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+a = 5
+#...input or change a here
+assert a == 42 # throws an AssertionError when a is not 42
+assert a == 42, "Error message" # throws an AssertionError
+       # when a is not 42 with "Error message" for the message
+       # the error message can be any expression

Task/Assertions/R/assertions.r

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+stopifnot(a==42)

Task/Assertions/REXX/assertions.rexx

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+/* REXX ***************************************************************
+* There's no assert feature in Rexx. That's how I'd implement it
+* 10.08.2012 Walter Pachl
+**********************************************************************/
+x.=42
+x.2=11
+Do i=1 By 1
+  Call assert x.i,42
+  End
+Exit
+assert:
+  Parse Arg assert_have,assert_should_have
+  If assert_have\==assert_should_have Then Do
+    Say 'Assertion fails in line' sigl
+    Say 'expected:' assert_should_have
+    Say '   found:' assert_have
+    Say sourceline(sigl)
+    Say 'Look around'
+    Trace ?R
+    Nop
+    Signal Syntax
+    End
+  Return
+Syntax: Say 'program terminated'

Task/Assertions/Racket/assertions-2.rkt

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+#lang racket
+
+(define x 80)
+(unless (= x 42)
+  (error "a is not 42")) ; will error

Task/Assertions/Racket/assertions.rkt

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+#lang racket
+
+(define/contract x
+  (=/c 42) ; make sure x = 42
+  42)
+
+(define/contract f
+  (-> number? (or/c 'yes 'no)) ; function contract
+  (lambda (x)
+    (if (= 42 x) 'yes 'no)))
+
+(f 42)    ; succeeds
+(f "foo") ; contract error!

Task/Assertions/Ruby/assertions.rb

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+require "test/unit/assertions"
+include Test::Unit::Assertions
+
+n = 5
+begin
+  assert_equal(42, n)
+rescue Exception => e
+  # Ruby 1.8: e is a Test::Unit::AssertionFailedError
+  # Ruby 1.9: e is a MiniTest::Assertion
+  puts e
+end

Task/Assertions/Sather/assertions.sa

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+class MAIN is
+  main is
+    i ::= 41;
+    assert i = 42; -- fatal
+    -- ...
+  end;
+end;

Task/Assertions/Scala/assertions-2.scala

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+require(a == 42)
+require(a == 42, "a isn't equal to 42")

Task/Assertions/Scala/assertions-3.scala

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+println(a.ensuring(a == 42))
+println(a.ensuring(a == 42, "a isn't equal to 42"))
+println(a.ensuring(_ == 42))
+println(a.ensuring(_ == 42, "a isn't equal to 42"))

Task/Assertions/Scala/assertions.scala

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+assert(a == 42)
+assert(a == 42, "a isn't equal to 42")
+assume(a == 42)
+assume(a == 42, "a isn't equal to 42")

Task/Assertions/Scheme/assertions.ss

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+(let ((x 42))
+  (assert (and (integer? x) (= x 42))))

Task/Assertions/Smalltalk/assertions-2.st

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+self assert: (... somethingMustEvaluateToTrue.. )
+self should:[ some code ] raise: someException "ensures that an exception is raised

Task/Assertions/Smalltalk/assertions-3.st

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+self assert: (... somethingMustEvaluateToTrue.. ) "implemented in Object"

Task/Assertions/Smalltalk/assertions.st

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+foo := 41.
+...
+self assert: (foo == 42).

Task/Assertions/Tcl/assertions.tcl

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+package require control
+
+set x 5
+control::assert {$x == 42}