Runtime evaluation/In an environment: Difference between revisions

=={{header|Phix}}==

See [[Runtime_evaluation#Phix]] for more details, or the docs.<br>

Evaluation occurs in a brand new context, and x must be explicitly provided/returned.

Note that nothing can escape the eval context: while x is not "global" here but could

trivially (/technically) be made one by prefixing its definition with "global", it would

still not escape the eval() context, and still have to be explicitly requested as a

return value, as per the second {"x"} parameter [aka rset] to eval().

<!--<lang Phix>(phixonline)-->

<span style="color: #008080;">without</span> <span style="color: #008080;">javascript_semantics</span>

<span style="color: #7060A8;">requires</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"1.0.1"</span><span style="color: #0000FF;">)</span>

<span style="color: #008080;">include</span> <span style="color: #7060A8;">eval</span><span style="color: #0000FF;">.</span><span style="color: #000000;">e</span>

<span style="color: #008080;">function</span> <span style="color: #000000;">eval_with_x</span><span style="color: #0000FF;">(</span><span style="color: #004080;">string</span> <span style="color: #000000;">expr</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">integer</span> <span style="color: #000000;">a</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">b</span><span style="color: #0000FF;">)</span>

<span style="color: #008080;">return</span> <span style="color: #7060A8;">eval</span><span style="color: #0000FF;">(</span><span style="color: #000000;">expr</span><span style="color: #0000FF;">,{</span><span style="color: #008000;">"x"</span><span style="color: #0000FF;">},{{</span><span style="color: #008000;">"x"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">b</span><span style="color: #0000FF;">}})[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">-</span>

<span style="color: #7060A8;">eval</span><span style="color: #0000FF;">(</span><span style="color: #000000;">expr</span><span style="color: #0000FF;">,{</span><span style="color: #008000;">"x"</span><span style="color: #0000FF;">},{{</span><span style="color: #008000;">"x"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">a</span><span style="color: #0000FF;">}})[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span>

<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>

<span style="color: #0000FF;">?</span><span style="color: #000000;">eval_with_x</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"integer x = power(2,x)"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,</span><span style="color: #000000;">5</span><span style="color: #0000FF;">)</span>

<!--</lang>-->

{{out}}

(As in 2<small>⁵</small> - 2<small>³</small> === 32 - 8 === 24)

<pre>

24

</pre>