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Revision as of 10:45, 25 October 2022

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=={{header|Phix}}==
{{libheader|Phix/basics}}
Phix supports named and optional parameters in a very simple, natural, and intuitive way, erring on the side of caution when faced with any potential ambiguity.<br>
Optional parameters are specified simply byany providingwith a default, and any non-defaulted parameters must occur before (to the left of) any defaulted parameterssuch.<br>
Named parameters can be given (when invoking a routine)provided in any order, but must be grouped together after (to the right of) any non-namedpositional parameters.<br>
Note that low-level builtins (those defined using AutoAsm() in psym.e/syminit()) do not [yet] support named parameters (maybe one day..), but everything else does.
 
The classic example (inspired by the standard Python equivalent) is that builtins\timedate.e defines:
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<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
<span style="color: #008080;">include</span> <span style="color: #004080;">timedate</span><span style="color: #0000FF;">.</span><span style="color: #000000;">e</span>
<span style="color: #008080;">constant</span> <span style="color: #000000;">fourdaysdays</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8000000;">timedelta1</span><span style="color: #0000FF;">(,</span> <span style="color: #000000;">dayshours</span> <span style="color: #0000FF;">:=</span> <span style="color: #000000;">47</span><span style="color: #0000FF;">),</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span> <span style="color: #000000;">1fourdays</span> <span style="color: #0000FF;">,=</span> <span style="color: #0080007060A8;">"wrong = %s\n"timedelta</span><span style="color: #0000FF;">,{(</span><span style="color: #7060A8000000;">elapseddays</span><span style="color: #0000FF;">(:=</span><span style="color: #000000;">oneday4</span><span style="color: #0000FF;">)}),</span>▼
<span style="color: #000080;font-style:italic;">-- fourdays = timedelta(0,4) -- equivalent, **NB** a plain '=' is a very different thing:</span>
<span style="color: #008080;">constant</span> <span style="color: #000000;">onedayslipup</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">timedelta</span><span style="color: #0000FF;">(</span><span style="color: #000000;">days</span><span style="color: #0000FF;">=</span><span style="color: #000000;">4</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- equivalent to=== timedelta([weeks:=]iff((equal(days,4)?true:false))▼
-- - with an error if no local/in scope variableidentifier days exists.</span>▼
<span style="color: #008080;">constant</span> <span style="color: #000000;">shift</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">timedelta</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hours</span><span style="color: #0000FF;">:=</span><span style="color: #000000;">hours</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- perfectly valid (param hours:=local hours)▼
-- timedelta(0,hours:=15,3) -- illegal (it is not clear whether you meant days:=3 or minutes:=3)</span>▼
-- though of course the weeks:=0 part is fine</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"fourdays = %s\n"</span><span style="color: #0000FF;">,{</span><span style="color: #7060A8;">elapsed</span><span style="color: #0000FF;">(</span><span style="color: #000000;">fourdays</span><span style="color: #0000FF;">)})</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"wrong = %s\n"</span><span style="color: #0000FF;">,{</span><span style="color: #7060A8;">elapsed</span><span style="color: #0000FF;">(</span><span style="color: #000000;">slipup</span><span style="color: #0000FF;">)})</span>
<span style="color: #000080;font-style:italic;">-- **NB** a plain '=' is a very different thing:</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">days</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span>
▲ <span style="color: #008080;">constant</span> <span style="color: #000000;">oneday</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">timedelta</span><span style="color: #0000FF;">(</span><span style="color: #000000;">days</span><span style="color: #0000FF;">=</span><span style="color: #000000;">4</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- equivalent to timedelta([weeks:=]iff((equal(days,4)?true:false))
▲ -- - with an error if no local variable days exists.</span>
▲ <span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"wrong = %s\n"</span><span style="color: #0000FF;">,{</span><span style="color: #7060A8;">elapsed</span><span style="color: #0000FF;">(</span><span style="color: #000000;">oneday</span><span style="color: #0000FF;">)})</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">hours</span><span style="color: #0000FF;">=</span><span style="color: #000000;">7</span>
▲ <span style="color: #008080;">constant</span> <span style="color: #000000;">shift</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">timedelta</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hours</span><span style="color: #0000FF;">:=</span><span style="color: #000000;">hours</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- perfectly valid (param hours:=local hours)
▲ -- timedelta(0,hours:=15,3) -- illegal (it is not clear whether you meant days:=3 or minutes:=3)</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"shift = %s\n"</span><span style="color: #0000FF;">,{</span><span style="color: #7060A8;">elapsed</span><span style="color: #0000FF;">(</span><span style="color: #000000;">shift</span><span style="color: #0000FF;">)})</span>
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