Such a macro is easy to implement in Common Lisp and similar dialects. In TXR Lisp, the standard macro-time macro evaluates an expression at macro-expansion time, and replaces it by its result, which is then treated as a literal (because the macro inserts `quote` around it, if required). Object Main extends " ( 0 ) push1 0 # "3628800" ( 2 ) doneĪs you can see, that expression was transformed into just a push of the results (and an instruction to mark the end of the bytecode segment). You can do any calculation you want before or after, create constants. If that intput creates function or methods, it creates and compile them. Not easy to define "compile time" with Oforth : oforth interpreter read input and perform it. The assembler output (cleaned up and demangled a little) shows exactly what's expected, stored as dataĪnd converting the tagged int to regular int we getĮxample.ml is compiled with ocaml.4.12.0+flambda (2021) the unrolling annotation is older than that, compilers as old as 4.03.0+flambda (2016) support it. Let fact10 = let rec factorial n = if n = 1 then n else n * factorial ( n - 1 ) in ( factorial unrolled 10 ]) 10 (* The unrolled annotation is what allows flambda to keep reducing the call * Beware that the number of unrollings must be greater than or equal to the * number of iterations (recursive calls) for this to compile down to a constant. to inline it in the resulting source code) For example, the following macro computes the factorial of n (a literal constant) and returns the value (e.g.
#GNU TIMECODE CALCULATOR CODE#
Julia includes a powerful macro feature that can perform arbitrary code transformations at compile-time (or technically at parse-time), and can also execute arbitrary Julia code. (Please don't actually save changes though.) If you are using View Source, you might want to do that in a new tab (so you also stay here with this view) and use your browser's search capability to quickly scroll to this location in the source view. To work around this issue, and see the original display, you can currently use either the "Edit" or "View Source" option, depending on whether you are logged in to rosettacode with an account that has edit rights here. Note: Currently, the mediawiki implementation is corrupting the above display due to a cascading sequence of bad design decisions and mis-interpreted specifications on the part of someone "contributing" to that implementation. Overwriting the above interlude except the factorial] T2Z [resume normal loading at relative location 2, The next control combination starts execution.]Į9Z
[At this point the interlude has been loaded but not executed. T#Z PF [Demo of calculating a constant in an interlude at load time. The interlude in the demo program below is based on a shorter example in Wilkes, Wheeler & Gill, 1951 edn, p. Also, if the multiplier register is used, its original value should be restored before exit from the interlude. the library subroutine M3 ran as an interlude it printed a header on the teleprinter, and then M3 and the header text were overwritten.Ĭode for an interlude should not change locations in the initial orders. Interludes could be used for calculation or for other purposes. In this way once-only code was not left taking up storage space, which was in short supply on EDSAC. Code that was used only by the interlude could then be overwritten. When finished, the interlude passed control back to initial orders, and normal loading was resumed. Code for an interlude was loaded into store, then loading was paused while the interlude was executed.
Under David Wheeler's Initial Orders 2, the effect of compile-time calculation could be achieved on EDSAC by the use of "interludes" in the loading process. ( define-constant DIX! ( factorial 10 )) ( define-constant DIX!+1 ( 1 + DIX! )) ( writeln DIX!+1 ) 3628801 EDSAC order code
The D compiler is able to run many functions at compile-time Compile Time Function Execution (CTFE): It will be treated as if it were declared SPECIAL. > (defun test-nonconstant () (factorial a)) > (defun test-constant () (factorial 10)) > (define-compiler-macro factorial (&whole form arg) Test with CLISP (taking advantage of its ! function) showing how a factorial call with a constant argument of 10 ends up compiled to the constant 3268800, but a factorial call with the argument a is compiled to a variable access and function call: ( define-compiler-macro factorial ( &whole form arg ) ( if ( constantp arg ) ( factorial arg ) form ))
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