22 lines
1.9 KiB
Rexx
22 lines
1.9 KiB
Rexx
/*REXX program implements and displays a stateless Y combinator. */
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numeric digits 1000 /*allow big numbers. */
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say ' fib' Y(fib (50)) /*Fibonacci series. */
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say ' fib' Y(fib (12 11 10 9 8 7 6 5 4 3 2 1 0)) /*Fibonacci series. */
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say ' fact' Y(fact (60)) /*single factorial*/
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say ' fact' Y(fact (0 1 2 3 4 5 6 7 8 9 10 11)) /*single factorial*/
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say ' Dfact' Y(dfact (4 5 6 7 8 9 10 11 12 13)) /*double factorial*/
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say ' Tfact' Y(tfact (4 5 6 7 8 9 10 11 12 13)) /*triple factorial*/
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say ' Qfact' Y(qfact (4 5 6 7 8 40)) /*quadruple factorial*/
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say ' length' Y(length (when for to where whenceforth)) /*lengths of words.*/
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say 'reverse' Y(reverse (23 678 1007 45 MAS I MA)) /*reverses strings. */
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say ' trunc' Y(trunc (-7.0005 12 3.14159 6.4 78.999)) /*truncates numbers. */
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exit /*stick a fork in it, we're all done. */
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/*────────────────────────────────────────────────────────────────────────────*/
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Y: parse arg Y _; $= /*the Y combinator.*/
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do j=1 for words(_); interpret '$=$' Y"("word(_,j)')'; end; return $
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fib: procedure; parse arg x; if x<2 then return x; s=0; a=0; b=1
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s=0; a=0; b=1; do j=2 to x; s=a+b; a=b; b=s; end; return s
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dfact: procedure; parse arg x; !=1; do j=x to 2 by -2; !=!*j; end; return !
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tfact: procedure; parse arg x; !=1; do j=x to 2 by -3; !=!*j; end; return !
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qfact: procedure; parse arg x; !=1; do j=x to 2 by -4; !=!*j; end; return !
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fact: procedure; parse arg x; !=1; do j=2 to x ; !=!*j; end; return !
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