diff options
Diffstat (limited to 'system/doc/reference_manual/expressions.xml')
| -rw-r--r-- | system/doc/reference_manual/expressions.xml | 47 |
1 files changed, 33 insertions, 14 deletions
diff --git a/system/doc/reference_manual/expressions.xml b/system/doc/reference_manual/expressions.xml index cf2d5034aa..ea3b2159fc 100644 --- a/system/doc/reference_manual/expressions.xml +++ b/system/doc/reference_manual/expressions.xml @@ -4,7 +4,7 @@ <chapter> <header> <copyright> - <year>2003</year><year>2017</year> + <year>2003</year><year>2018</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -567,6 +567,10 @@ Expr1 <input>op</input> Expr2</pre> order is defined:</p> <pre> number < atom < reference < fun < port < pid < tuple < map < nil < list < bit string</pre> + <p><c>nil</c> in the previous expression represents the empty list + (<c>[]</c>), which is regarded as a separate type from + <c>list/0</c>. That is why <c>nil < list</c>. + </p> <p>Lists are compared element by element. Tuples are ordered by size, two tuples with the same size are compared element by element.</p> @@ -574,6 +578,7 @@ number < atom < reference < fun < port < pid < tuple < map ascending term order and then by values in key order. In maps key order integers types are considered less than floats types. </p> + <p>Atoms are compared using their string value, codepoint by codepoint.</p> <p>When comparing an integer to a float, the term with the lesser precision is converted into the type of the other term, unless the operator is one of <c>=:=</c> or <c>=/=</c>. A float is more precise than @@ -1216,10 +1221,10 @@ Ei = Value | <<1,17,0,42>> 10> <input>H.</input> <<17,0,42>> -11> <input><<G,H/bitstring>> = <<1,17,42:12>>.</input> -<<1,17,1,10:4>> -12> <input>H.</input> -<<17,1,10:4>> +11> <input><<G,J/bitstring>> = <<1,17,42:12>>.</input> +<<1,17,2,10:4>> +12> <input>J.</input> +<<17,2,10:4>> 13> <input><<1024/utf8>>.</input> <<208,128>> </pre> @@ -1340,9 +1345,9 @@ hello</pre> <code type="none"> try Exprs catch - [Class1:]ExceptionPattern1 [when ExceptionGuardSeq1] -> + Class1:ExceptionPattern1[:Stacktrace] [when ExceptionGuardSeq1] -> ExceptionBody1; - [ClassN:]ExceptionPatternN [when ExceptionGuardSeqN] -> + ClassN:ExceptionPatternN[:Stacktrace] [when ExceptionGuardSeqN] -> ExceptionBodyN end</code> <p>This is an enhancement of @@ -1362,10 +1367,12 @@ end</code> the evaluation. In that case the exception is caught and the patterns <c>ExceptionPattern</c> with the right exception class <c>Class</c> are sequentially matched against the caught - exception. An omitted <c>Class</c> is shorthand for <c>throw</c>. - If a match succeeds and the optional guard sequence + exception. If a match succeeds and the optional guard sequence <c>ExceptionGuardSeq</c> is true, the corresponding <c>ExceptionBody</c> is evaluated to become the return value.</p> + <p><c>Stacktrace</c>, if specified, must be the name of a variable + (not a pattern). The stack trace is bound to the variable when + the corresponding <c>ExceptionPattern</c> matches.</p> <p>If an exception occurs during evaluation of <c>Exprs</c> but there is no matching <c>ExceptionPattern</c> of the right <c>Class</c> with a true guard sequence, the exception is passed @@ -1373,6 +1380,18 @@ end</code> expression.</p> <p>If an exception occurs during evaluation of <c>ExceptionBody</c>, it is not caught.</p> + <p>It is allowed to omit <c>Class</c> and <c>Stacktrace</c>. + An omitted <c>Class</c> is shorthand for <c>throw</c>:</p> + + <code type="none"> +try Exprs +catch + ExceptionPattern1 [when ExceptionGuardSeq1] -> + ExceptionBody1; + ExceptionPatternN [when ExceptionGuardSeqN] -> + ExceptionBodyN +end</code> + <p>The <c>try</c> expression can have an <c>of</c> section: </p> @@ -1384,10 +1403,10 @@ try Exprs of PatternN [when GuardSeqN] -> BodyN catch - [Class1:]ExceptionPattern1 [when ExceptionGuardSeq1] -> + Class1:ExceptionPattern1[:Stacktrace] [when ExceptionGuardSeq1] -> ExceptionBody1; ...; - [ClassN:]ExceptionPatternN [when ExceptionGuardSeqN] -> + ClassN:ExceptionPatternN[:Stacktrace] [when ExceptionGuardSeqN] -> ExceptionBodyN end</code> <p>If the evaluation of <c>Exprs</c> succeeds without an exception, @@ -1408,10 +1427,10 @@ try Exprs of PatternN [when GuardSeqN] -> BodyN catch - [Class1:]ExceptionPattern1 [when ExceptionGuardSeq1] -> + Class1:ExceptionPattern1[:Stacktrace] [when ExceptionGuardSeq1] -> ExceptionBody1; ...; - [ClassN:]ExceptionPatternN [when ExceptionGuardSeqN] -> + ClassN:ExceptionPatternN[:Stacktrace] [when ExceptionGuardSeqN] -> ExceptionBodyN after AfterBody @@ -1470,7 +1489,7 @@ try Expr catch throw:Term -> Term; exit:Reason -> {'EXIT',Reason} - error:Reason -> {'EXIT',{Reason,erlang:get_stacktrace()}} + error:Reason:Stk -> {'EXIT',{Reason,Stk}} end</code> </section> |