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Runtime evaluation/In an environment: Difference between revisions
Runtime evaluation/In an environment (view source)
Revision as of 11:24, 30 April 2009
, 15 years ago→{{header|Tcl}}: provide another solution for clarified requirements
(→{{header|Octave}}: add note about nonglobalness) |
(→{{header|Tcl}}: provide another solution for clarified requirements) |
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=={{header|Tcl}}==
<lang tcl>proc eval_twice {func a b} {▼
▲proc eval_twice {func a b} {
set x $a
set 1st [expr $func]
set x $b
set 2nd [expr $func]
expr {$2nd - $1st}
}
puts [eval_twice {2 ** $x} 3 5] ;# ==> 24</lang>
Here's another take, similar to other answers. It passes a code block to be <code>eval</code>ed, not just an expression for <code>expr</code>
<lang tcl>proc eval_with_x {code val1 val2} {
expr {[set x $val2; eval $code] - [set x $val1; eval $code]}
}
eval_with_x {expr {2**$x}} 3 5 ;# ==> 24</lang>
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