Runtime evaluation/In an environment: Difference between revisions
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→{{header|Metafont}}: if the problem was the "global" variable... fixed (as tcl, similar to php) |
trying to clarify some more... |
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{{task}} Given a program in the language with a free variable named <var>x</var> (or another name if that is not valid syntax), evaluate it with <var>x</var> bound to a provided value, then evaluate it again with <var>x</var> bound to another provided value, then subtract the result of the first from the second and return or print it. |
{{task}} Given a program in the language (as a string or AST) with a free variable named <var>x</var> (or another name if that is not valid syntax), evaluate it with <var>x</var> bound to a provided value, then evaluate it again with <var>x</var> bound to another provided value, then subtract the result of the first from the second and return or print it. |
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Do so in a way which: |
Do so in a way which: |
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* does not involve string manipulation of source code |
* does not involve string manipulation of the input source code |
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* is plausibly extensible to a runtime-chosen set of bindings rather than just <var>x</var> |
* is plausibly extensible to a runtime-chosen set of bindings rather than just <var>x</var> |
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* does not make <var>x</var> a ''global'' variable |
* does not make <var>x</var> a ''global'' variable |