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General recursive function

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3329: 1843: 2473: 1504: 1049: 139:. While all primitive recursive functions are total, this is not true of partial recursive functions; for example, the minimisation of the successor function is undefined. The primitive recursive functions are a subset of the total recursive functions, which are a subset of the partial recursive functions. For example, the 3118: 2218: 2925: 1838:{\displaystyle {\begin{aligned}\rho (g,h)&\ {\stackrel {\mathrm {def} }{=}}\ f\quad {\text{where the k+1 -ary function }}f{\text{ is defined by}}\\f(0,x_{1},\ldots ,x_{k})&=g(x_{1},\ldots ,x_{k})\\f(S(y),x_{1},\ldots ,x_{k})&=h(y,f(y,x_{1},\ldots ,x_{k}),x_{1},\ldots ,x_{k})\,.\end{aligned}}} 3367:
that do not terminate for certain inputs and an undefined result for that input in the corresponding partial recursive function. The unbounded search operator is not definable by the rules of primitive recursion as those do not provide a mechanism for "infinite loops" (undefined values).
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A number of different symbolisms are used in the literature. An advantage to using the symbolism is a derivation of a function by "nesting" of the operators one inside the other is easier to write in a compact form. In the following the string of parameters
125:) are partial functions that take finite tuples of natural numbers and return a single natural number. They are the smallest class of partial functions that includes the initial functions and is closed under composition, primitive recursion, and the 3723:
To construct U is to write down the definition of a general-recursive function U(n, x) that correctly interprets the number n and computes the appropriate function of x. to construct U directly would involve essentially the same amount of effort,
2468:{\displaystyle {\begin{aligned}\mu (f)(x_{1},\ldots ,x_{k})=z{\stackrel {\mathrm {def} }{\iff }}\ f(i,x_{1},\ldots ,x_{k})&>0\quad {\text{for}}\quad i=0,\ldots ,z-1\quad {\text{and}}\\f(z,x_{1},\ldots ,x_{k})&=0\quad \end{aligned}}} 2946: 2805: 578: 273: 1352: 3667: 1227: 792: 2482:
Intuitively, minimisation seeks—beginning the search from 0 and proceeding upwards—the smallest argument that causes the function to return zero; if there is no such argument, or if one encounters an argument for which
75:, and their inductive definition (below) builds upon that of the primitive recursive functions. However, not every total recursive function is a primitive recursive function—the most famous example is the 2719: 2739:
The following examples are intended just to demonstrate the use of the minimization operator; they could also be defined without it, albeit in a more complicated way, since they are all primitive recursive.
2071: 2585:). The only difference is, that it becomes undecidable whether a specific function definition defines a μ-recursive function, as it is undecidable whether a computable (i.e. μ-recursive) function is total. 361: 4495: 1044:{\displaystyle h\circ (g_{1},\ldots ,g_{m})\ {\stackrel {\mathrm {def} }{=}}\ f,\quad {\text{where}}\quad f(x_{1},\ldots ,x_{k})=h(g_{1}(x_{1},\ldots ,x_{k}),\ldots ,g_{m}(x_{1},\ldots ,x_{k})).} 2223: 1509: 2581:
only. Although this restricts the μ-operator as compared to the definition given here, the class of μ-recursive functions remains the same, which follows from Kleene's Normal Form Theorem (see
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turns out to coincide with the class of the Turing-computable functions introduced by Alan Turing as well as with the class of the λ-definable functions introduced by Alonzo Church.
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defined by an operator is the set of the values of the arguments such that every function application that must be done during the computation provides a well-defined result):
3689:. A consequence of this result is that any μ-recursive function can be defined using a single instance of the μ operator applied to a (total) primitive recursive function. 3258: 3172: 2800: 3113:{\displaystyle (\operatorname {Not} \circ \operatorname {Gt} \circ (\operatorname {Mul} \circ (S\circ P_{1}^{2},S\circ P_{1}^{2}),P_{2}^{2}))\;(z,x)=(\lnot S(z)*S(z)>x)} 463: 2920:{\displaystyle \operatorname {Isqrt} =\mu (\operatorname {Not} \circ \operatorname {Gt} \circ (\operatorname {Mul} \circ (S\circ P_{1}^{2},S\circ P_{1}^{2}),P_{2}^{2}))} 401: 616: 2612: 2514: 2209: 2100: 3412: 4145:: Kleene gives an example of how to perform the recursive derivation of f(b, a) = b + a (notice reversal of variables a and b). He starts with 3 initial functions 431: 135:
The smallest class of functions including the initial functions and closed under composition and primitive recursion (i.e. without minimisation) is the class of
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as a primitive function that always returns zero, and build the constant functions from the zero function, the successor function and the composition operator.
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The following examples define general recursive functions that are not primitive recursive; hence they cannot avoid using the minimization operator.
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Kfoury, A. J., R. N. Moll, and M. A. Arbib, A Programming Approach to Computability, 2nd ed., Springer-Verlag, Berlin, Heidelberg, New York, 1982
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holds if and only if for any choice of arguments either both functions are defined and their values are equal or both functions are undefined.
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Jones, N. D., Computability and Complexity: From a Programming Perspective, The MIT Press, Cambridge, Massachusetts, London, England, 1997
2628: 4764: 1968: 297: 3811:: Kleene uses x' and S for "Successor". As "successor" is considered to be primitive, most texts use the apostrophe as follows: 4747: 4463: 4933: 4751: 4295: 60: 4278: 4911: 4866: 4844: 4823: 4616: 3377: 4743: 2733: 4420: 4041:(base step, induction step) " where n indicates the number of variables, B-B-J use " Pr(base step, induction step)( 4556: 4499: 3417: 1432: 4665: 4394: 3340: 102: 4533: 2119: 4953: 3177: 3485: 2573:
While some textbooks use the μ-operator as defined here, others like demand that the μ-operator is applied to
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Boolos, G. S., Burgess, J. P., Jeffrey, R. C., Computability and Logic, Cambridge University Press, 2007
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Recursively enumerable sets and degrees: A Study of Computable Functions and Computably Generated Sets
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can be used to compare partial μ-recursive functions. This is defined for all partial functions
63:, it is shown that the μ-recursive functions are precisely the functions that can be computed by 374: 600: 4899: 4099:
induction step: f( b' , a ) = ( f ( b, a ) )' = g( b, f( b, a), a ) = g( b, c, a ) = c' = S(U
2597: 2490: 2185: 2076: 4834: 3387: 4236: 3307: 588: 3310:. There is no way to computably tell if a given general recursive function is total - see 8: 4928: 2746: 573:{\displaystyle P_{i}^{k}(x_{1},\ldots ,x_{k})\ {\stackrel {\mathrm {def} }{=}}\ x_{i}\,.} 410: 48: 4299: 4382: 4374: 3698: 3360: 140: 76: 20: 4784: 4907: 4862: 4840: 4819: 4316: 4878: 4854: 4779: 4386: 4366: 4334: 4248: 4231: 2940: 87: 40: 24: 4934:
A compiler for transforming a recursive function into an equivalent Turing machine
4338: 4320: 268:{\displaystyle C_{n}^{k}(x_{1},\ldots ,x_{k})\ {\stackrel {\mathrm {def} }{=}}\ n} 4895: 4891: 3312: 2590: 83: 1347:{\displaystyle h(g_{1}(x_{1},\ldots ,x_{k}),\ldots ,g_{m}(x_{1},\ldots ,x_{k}))} 47:
to natural numbers that is "computable" in an intuitive sense – as well as in a
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if it is defined for every input, or, equivalently, if it can be computed by a
106: 64: 44: 3770:) = q " and Boolos-Burgess-Jeffrey (2002) (B-B-J) use the abbreviation " const 3662:{\displaystyle f(x_{1},\ldots ,x_{k})\simeq U(\mu (T)(e,x_{1},\ldots ,x_{k}))} 1222:{\displaystyle g_{1}(x_{1},\ldots ,x_{k}),\ldots ,g_{m}(x_{1},\ldots ,x_{k}),} 4942: 4887: 4881:
model, thus demonstrating its equivalence to the general recursive functions.
3692: 787:{\displaystyle g_{1}(x_{1},\ldots ,x_{k}),\ldots ,g_{m}(x_{1},\ldots ,x_{k})} 126: 4700:
Enderton, H. B., A Mathematical Introduction to Logic, Academic Press, 1972
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In a similar manner, but without the sub- and superscripts, B-B-J write:
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On pages 210-215 Minsky shows how to create the μ-operator using the
4253: 2802:. Using the minimization operator, a general recursive definition is 4370: 3728:, as we have invested in constructing the universal Turing machine 2714:{\displaystyle f(x_{1},\ldots ,x_{k})\simeq g(x_{1},\ldots ,x_{l})} 3319: 3261: 2732:
Examples not involving the minimization operator can be found at
2066:{\displaystyle h(z,f(z,x_{1},\ldots ,x_{k}),x_{1},\ldots ,x_{k})} 3715:
defined above is in essence the μ-recursive equivalent of the
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can be proven to be total recursive, and to be non-primitive.
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One of several equivalent definitions of a computable function
4708: 4706: 4906:(4th ed.). Cambridge University Press. pp. 70–71. 356:{\displaystyle S(x)\ {\stackrel {\mathrm {def} }{=}}\ x+1\,} 2943:, greater-than, and multiplication, respectively. In fact, 82:
Other equivalent classes of functions are the functions of
4703: 3953:", whereas the subscript "n" refers to the n variable "x 3849:" to indicate the identity function over the variables x 4673: 4598: 4538: 4490:{\displaystyle \lambda {\mbox{-}}K{\mbox{-definable}}} 4481: 4471: 4402: 4285:. Metaphysics Research Lab, Stanford University. 2021. 2487:
is not defined, then the search never terminates, and
4792: 4668: 4619: 4593: 4559: 4536: 4502: 4466: 4423: 4397: 3949:). The superscript "m" refers to the m of function "f 3701: 3555: 3488: 3420: 3390: 3216: 3180: 3130: 2949: 2808: 2763: 2631: 2600: 2522: 2493: 2221: 2188: 2122: 2079: 1971: 1916: 1855: 1507: 1435: 1375: 1235: 1116: 1061: 804: 684: 628: 603: 475: 439: 413: 377: 300: 181: 71:). The μ-recursive functions are closely related to 4886: 4762: 4681: 4655: 4606: 4580: 4546: 4523: 4489: 4453: 4410: 4082:Example: primitive recursion definition of a + b: 3707: 3661: 3530: 3474: 3406: 3252: 3198: 3166: 3112: 2919: 2794: 2713: 2606: 2563: 2508: 2467: 2203: 2170: 2094: 2065: 1957: 1902: 1837: 1489: 1417: 1346: 1221: 1102: 1043: 786: 670: 610: 572: 457: 425: 395: 355: 267: 4772:Transactions of the American Mathematical Society 4204:induction step: h( b', a ) = g( b, h( b, a ), a ) 3527: 3471: 3403: 4940: 4355:(Dec 1937). "Computability and λ-Definability". 51:. If the function is total, it is also called a 4748:Primitive recursive function#Equality predicate 4696: 4694: 4656:{\displaystyle {\stackrel {Kleene}{\implies }}} 3945:(not to be confused with his S for "successor" 67:(this is one of the theorems that supports the 3320:Equivalence with other models of computability 4454:{\displaystyle {\stackrel {triv}{\implies }}} 4720: 4718: 4691: 4581:{\displaystyle {\stackrel {161}{\implies }}} 4524:{\displaystyle {\stackrel {160}{\implies }}} 3475:{\displaystyle T(y,e,x_{1},\ldots ,x_{k})\!} 1490:{\displaystyle h(y,z,x_{1},\ldots ,x_{k})\,} 4752:Primitive recursive function#Multiplication 4682:{\displaystyle \lambda {\mbox{-definable}}} 4411:{\displaystyle \lambda {\mbox{-definable}}} 3297: 4628: 4624: 4568: 4564: 4547:{\displaystyle {\mbox{Turing computable}}} 4511: 4507: 4432: 4428: 3049: 2287: 2283: 2171:{\displaystyle f(y,x_{1},\ldots ,x_{k})\,} 86:and the functions that can be computed by 4929:Stanford Encyclopedia of Philosophy entry 4859:Computation: Finite and Infinite Machines 4818:. Walters-Noordhoff & North-Holland. 4783: 4715: 3199:{\displaystyle \operatorname {Isqrt} (x)} 2167: 1827: 1486: 1414: 667: 607: 566: 352: 3531:{\displaystyle f(x_{1},\ldots ,x_{k})\!} 3384:there are primitive recursive functions 2582: 1903:{\displaystyle f(y,x_{1},\ldots ,x_{k})} 1418:{\displaystyle g(x_{1},\ldots ,x_{k})\,} 671:{\displaystyle h(x_{1},\ldots ,x_{m})\,} 4607:{\displaystyle \mu {\mbox{-recursive}}} 4283:The Stanford Encyclopedia of Philosophy 3482:such that for any μ-recursive function 3302:A general recursive function is called 4941: 4853: 4810: 4798: 4765:"Recursive predicates and quantifiers" 4351: 4315: 3371: 3361:equivalence of models of computability 2564:{\displaystyle (x_{1},\ldots ,x_{k}).} 1958:{\displaystyle g(x_{1},\ldots ,x_{k})} 1103:{\displaystyle f(x_{1},\ldots ,x_{k})} 279:Alternative definitions use instead a 4832: 4744:Primitive recursive function#Junctors 2734:Primitive recursive function#Examples 3853:; B-B-J use the identity function id 3323: 4296:Stanford Encyclopedia of Philosophy 3931:Composition (Substitution) operator 97:recursive functions with values in 13: 4321:"λ-definability and recursiveness" 3071: 2297: 2294: 2291: 1551: 1548: 1545: 865: 862: 859: 545: 542: 539: 332: 329: 326: 251: 248: 245: 14: 4965: 4922: 4861:. Prentice-Hall. pp. 210–5. 4785:10.1090/S0002-9947-1943-0007371-8 3380:due to Kleene says that for each 1568:where the k+1 -ary function  4763:Stephen Cole Kleene (Jan 1943). 3327: 2516:is not defined for the argument 146:Primitive or "basic" functions: 4816:Introduction to Metamathematics 4756: 2460: 2396: 2368: 2362: 1565: 888: 882: 103:computational complexity theory 4736: 4727: 4625: 4565: 4508: 4429: 4345: 4309: 4289: 4271: 3726:and essentially the same ideas 3656: 3653: 3615: 3612: 3606: 3600: 3591: 3559: 3524: 3492: 3468: 3424: 3400: 3394: 3363:, a parallel is drawn between 3253:{\displaystyle S(z)*S(z)>x} 3241: 3235: 3226: 3220: 3193: 3187: 3167:{\displaystyle S(z)*S(z)>x} 3155: 3149: 3140: 3134: 3107: 3098: 3092: 3083: 3077: 3068: 3062: 3050: 3046: 3043: 3022: 2974: 2965: 2950: 2914: 2911: 2890: 2842: 2833: 2818: 2795:{\displaystyle (z+1)^{2}>x} 2777: 2764: 2708: 2676: 2667: 2635: 2555: 2523: 2503: 2497: 2447: 2409: 2349: 2311: 2284: 2270: 2238: 2235: 2229: 2198: 2192: 2164: 2126: 2060: 2025: 1987: 1975: 1952: 1920: 1897: 1859: 1824: 1789: 1751: 1739: 1726: 1691: 1685: 1679: 1669: 1637: 1624: 1586: 1527: 1515: 1483: 1439: 1411: 1379: 1341: 1338: 1306: 1284: 1252: 1239: 1213: 1181: 1159: 1127: 1097: 1065: 1035: 1032: 1000: 978: 946: 933: 924: 892: 843: 811: 781: 749: 727: 695: 664: 632: 523: 491: 310: 304: 229: 197: 1: 4339:10.1215/s0012-7094-36-00227-2 4264: 4225: 458:{\displaystyle 1\leq i\leq k} 137:primitive recursive functions 112: 73:primitive recursive functions 4259:Recursion (computer science) 4087:base step: f( 0, a ) = a = U 3801:( r, s, t, u, v, w, x ) = 13 3794:( r, s, t, u, v, w, x ) = 13 3732: 2753:can be defined as the least 1360:Primitive recursion operator 7: 4242: 4037:: Kleene uses the symbol " 3925:( r, s, t, u, v, w, x ) = t 3542:free variables there is an 2727: 622:): Given an m-ary function 407:): For all natural numbers 123:general recursive functions 10: 4970: 3933:: Kleene uses a bold-face 164:: For each natural number 33:partial recursive function 29:general recursive function 4358:Journal of Symbolic Logic 4326:Duke Mathematical Journal 396:{\displaystyle P_{i}^{k}} 4391:Proof outline on p.153: 4190:base step: h( 0, a ) = U 4063:induction step: h( y+1, 3840:: Kleene (1952) uses " U 3717:universal Turing machine 3304:total recursive function 3298:Total recursive function 611:{\displaystyle \circ \,} 55:(sometimes shortened to 53:total recursive function 4904:Computability and Logic 2607:{\displaystyle \simeq } 2509:{\displaystyle \mu (f)} 2204:{\displaystyle \mu (f)} 2095:{\displaystyle z<y.} 4683: 4657: 4608: 4582: 4548: 4525: 4491: 4455: 4412: 3730: 3709: 3663: 3532: 3476: 3408: 3407:{\displaystyle U(y)\!} 3254: 3200: 3168: 3114: 2921: 2796: 2715: 2608: 2565: 2510: 2469: 2205: 2172: 2096: 2067: 1959: 1904: 1839: 1491: 1419: 1348: 1223: 1104: 1045: 788: 678:and m k-ary functions 672: 612: 574: 459: 427: 397: 357: 269: 127:minimization operator 4954:Theory of computation 4684: 4658: 4609: 4583: 4549: 4526: 4492: 4456: 4413: 4353:Turing, Alan Mathison 4279:"Recursive Functions" 3721: 3710: 3664: 3533: 3477: 3409: 3255: 3201: 3169: 3115: 2922: 2797: 2716: 2609: 2566: 2511: 2470: 2206: 2173: 2107:Minimization operator 2097: 2068: 1960: 1905: 1840: 1492: 1420: 1349: 1224: 1105: 1046: 789: 673: 620:substitution operator 613: 575: 460: 428: 398: 358: 289:Successor function S: 270: 119:μ-recursive functions 4949:Computability theory 4666: 4617: 4591: 4557: 4534: 4500: 4464: 4421: 4395: 4237:McCarthy 91 function 3862:over the variables x 3699: 3553: 3486: 3418: 3388: 3308:total Turing machine 3260:holds. The negation 3214: 3178: 3128: 2947: 2806: 2761: 2629: 2598: 2520: 2491: 2219: 2186: 2120: 2077: 2073:are defined for all 1969: 1914: 1853: 1505: 1433: 1373: 1233: 1114: 1059: 802: 682: 626: 601: 596:Composition operator 589:domain of a function 473: 437: 411: 375: 298: 179: 69:Church–Turing thesis 61:computability theory 37:μ-recursive function 4839:. Springer-Verlag. 4833:Soare, R. (1999) . 4300:Recursive Functions 4035:Primitive Recursion 3962:If we are given h( 3378:normal form theorem 3372:Normal form theorem 3042: 3021: 2997: 2910: 2889: 2865: 2747:integer square root 1910:is defined only if 1576: is defined by 1110:is defined only if 490: 426:{\displaystyle i,k} 392: 370:Projection function 196: 151:Constant functions 4900:"6.2 Minimization" 4679: 4677: 4653: 4604: 4602: 4578: 4544: 4542: 4521: 4487: 4485: 4475: 4451: 4408: 4406: 4317:Kleene, Stephen C. 3809:Successor function 3746:is abbreviated as 3705: 3659: 3528: 3472: 3404: 3339:. You can help by 3250: 3196: 3164: 3110: 3028: 3007: 2983: 2917: 2896: 2875: 2851: 2792: 2711: 2604: 2561: 2506: 2465: 2463: 2201: 2168: 2092: 2063: 1955: 1900: 1835: 1833: 1487: 1415: 1344: 1219: 1100: 1041: 784: 668: 608: 570: 476: 455: 423: 393: 378: 353: 265: 182: 141:Ackermann function 107:complexity class R 93:The subset of all 77:Ackermann function 57:recursive function 21:mathematical logic 4855:Minsky, Marvin L. 4676: 4650: 4601: 4575: 4541: 4540:Turing computable 4518: 4484: 4474: 4448: 4405: 4187:( b, c, a )) = c' 4052:base step: h( 0, 3838:Identity function 3757:: Kleene uses " C 3755:Constant function 3708:{\displaystyle U} 3685:for the function 3357: 3356: 3271:encodes truth by 3124:if, and only if, 2400: 2366: 2307: 2302: 2116:+1)-ary function 1577: 1569: 1561: 1556: 1534: 1429:+2 -ary function 886: 875: 870: 848: 618:(also called the 555: 550: 528: 405:Identity function 403:(also called the 342: 337: 315: 261: 256: 234: 88:Markov algorithms 4961: 4917: 4896:Jeffrey, Richard 4879:register machine 4872: 4850: 4829: 4802: 4796: 4790: 4789: 4787: 4769: 4760: 4754: 4740: 4734: 4731: 4725: 4722: 4713: 4710: 4701: 4698: 4689: 4688: 4686: 4685: 4680: 4678: 4674: 4662: 4660: 4659: 4654: 4652: 4651: 4649: 4629: 4622: 4613: 4611: 4610: 4605: 4603: 4599: 4587: 4585: 4584: 4579: 4577: 4576: 4574: 4569: 4562: 4553: 4551: 4550: 4545: 4543: 4539: 4530: 4528: 4527: 4522: 4520: 4519: 4517: 4512: 4505: 4496: 4494: 4493: 4488: 4486: 4482: 4476: 4472: 4460: 4458: 4457: 4452: 4450: 4449: 4447: 4433: 4426: 4417: 4415: 4414: 4409: 4407: 4403: 4390: 4349: 4343: 4342: 4313: 4307: 4293: 4287: 4286: 4275: 4249:Recursion theory 4232:Fibonacci number 4198: 4197: 4186: 4185: 4178:g(b, c, a) = S(U 4174: 4173: 4162: 4161: 4133: 4132: 4121: 4120: 4107: 4106: 4095: 4094: 4000: 3999: 3944: 3943: 3924: 3923: 3915: 3914: 3896: 3895: 3883: 3882: 3861: 3860: 3848: 3847: 3793: 3792: 3765: 3764: 3714: 3712: 3711: 3706: 3668: 3666: 3665: 3660: 3652: 3651: 3633: 3632: 3590: 3589: 3571: 3570: 3537: 3535: 3534: 3529: 3523: 3522: 3504: 3503: 3481: 3479: 3478: 3473: 3467: 3466: 3448: 3447: 3413: 3411: 3410: 3405: 3352: 3349: 3331: 3324: 3282: 3278: 3274: 3270: 3267:is needed since 3266: 3259: 3257: 3256: 3251: 3209: 3205: 3203: 3202: 3197: 3173: 3171: 3170: 3165: 3123: 3119: 3117: 3116: 3111: 3041: 3036: 3020: 3015: 2996: 2991: 2941:logical negation 2938: 2934: 2930: 2926: 2924: 2923: 2918: 2909: 2904: 2888: 2883: 2864: 2859: 2801: 2799: 2798: 2793: 2785: 2784: 2756: 2752: 2720: 2718: 2717: 2712: 2707: 2706: 2688: 2687: 2666: 2665: 2647: 2646: 2613: 2611: 2610: 2605: 2580: 2570: 2568: 2567: 2562: 2554: 2553: 2535: 2534: 2515: 2513: 2512: 2507: 2486: 2474: 2472: 2471: 2466: 2464: 2446: 2445: 2427: 2426: 2401: 2398: 2367: 2364: 2348: 2347: 2329: 2328: 2305: 2304: 2303: 2301: 2300: 2288: 2281: 2269: 2268: 2250: 2249: 2210: 2208: 2207: 2202: 2177: 2175: 2174: 2169: 2163: 2162: 2144: 2143: 2111: 2101: 2099: 2098: 2093: 2072: 2070: 2069: 2064: 2059: 2058: 2040: 2039: 2024: 2023: 2005: 2004: 1964: 1962: 1961: 1956: 1951: 1950: 1932: 1931: 1909: 1907: 1906: 1901: 1896: 1895: 1877: 1876: 1849:This means that 1844: 1842: 1841: 1836: 1834: 1823: 1822: 1804: 1803: 1788: 1787: 1769: 1768: 1725: 1724: 1706: 1705: 1668: 1667: 1649: 1648: 1623: 1622: 1604: 1603: 1578: 1575: 1570: 1567: 1559: 1558: 1557: 1555: 1554: 1542: 1537: 1532: 1496: 1494: 1493: 1488: 1482: 1481: 1463: 1462: 1424: 1422: 1421: 1416: 1410: 1409: 1391: 1390: 1364: 1354:are all defined. 1353: 1351: 1350: 1345: 1337: 1336: 1318: 1317: 1305: 1304: 1283: 1282: 1264: 1263: 1251: 1250: 1228: 1226: 1225: 1220: 1212: 1211: 1193: 1192: 1180: 1179: 1158: 1157: 1139: 1138: 1126: 1125: 1109: 1107: 1106: 1101: 1096: 1095: 1077: 1076: 1055:This means that 1050: 1048: 1047: 1042: 1031: 1030: 1012: 1011: 999: 998: 977: 976: 958: 957: 945: 944: 923: 922: 904: 903: 887: 884: 873: 872: 871: 869: 868: 856: 851: 846: 842: 841: 823: 822: 793: 791: 790: 785: 780: 779: 761: 760: 748: 747: 726: 725: 707: 706: 694: 693: 677: 675: 674: 669: 663: 662: 644: 643: 617: 615: 614: 609: 579: 577: 576: 571: 565: 564: 553: 552: 551: 549: 548: 536: 531: 526: 522: 521: 503: 502: 489: 484: 464: 462: 461: 456: 432: 430: 429: 424: 402: 400: 399: 394: 391: 386: 362: 360: 359: 354: 340: 339: 338: 336: 335: 323: 318: 313: 274: 272: 271: 266: 259: 258: 257: 255: 254: 242: 237: 232: 228: 227: 209: 208: 195: 190: 171: 167: 162: 161: 160: 130: 100: 41:partial function 25:computer science 4969: 4968: 4964: 4963: 4962: 4960: 4959: 4958: 4939: 4938: 4925: 4920: 4914: 4869: 4847: 4826: 4812:Kleene, Stephen 4806: 4805: 4801:, pp. 189. 4797: 4793: 4767: 4761: 4757: 4741: 4737: 4732: 4728: 4723: 4716: 4711: 4704: 4699: 4692: 4672: 4667: 4664: 4663: 4630: 4623: 4621: 4620: 4618: 4615: 4614: 4597: 4592: 4589: 4588: 4570: 4563: 4561: 4560: 4558: 4555: 4554: 4537: 4535: 4532: 4531: 4513: 4506: 4504: 4503: 4501: 4498: 4497: 4480: 4470: 4465: 4462: 4461: 4434: 4427: 4425: 4424: 4422: 4419: 4418: 4401: 4396: 4393: 4392: 4371:10.2307/2268280 4350: 4346: 4314: 4310: 4294: 4290: 4277: 4276: 4272: 4267: 4245: 4228: 4210:He arrives at: 4196: 4193: 4192: 4191: 4184: 4181: 4180: 4179: 4175:( b, c, a ) = c 4172: 4169: 4168: 4167: 4160: 4157: 4156: 4155: 4131: 4128: 4127: 4126: 4119: 4116: 4115: 4114: 4105: 4102: 4101: 4100: 4093: 4090: 4089: 4088: 4067:) = g( y, h(y, 4008: 4004: 3998: 3995: 3994: 3993: 3977: 3969: 3956: 3952: 3942: 3939: 3938: 3937: 3922: 3919: 3918: 3917: 3913: 3910: 3909: 3908: 3904: 3894: 3891: 3890: 3889: 3881: 3878: 3877: 3876: 3869: 3865: 3859: 3856: 3855: 3854: 3852: 3846: 3843: 3842: 3841: 3829: 3825: 3821: 3800: 3791: 3788: 3787: 3786: 3773: 3763: 3760: 3759: 3758: 3745: 3741: 3735: 3700: 3697: 3696: 3647: 3643: 3628: 3624: 3585: 3581: 3566: 3562: 3554: 3551: 3550: 3518: 3514: 3499: 3495: 3487: 3484: 3483: 3462: 3458: 3443: 3439: 3419: 3416: 3415: 3389: 3386: 3385: 3374: 3365:Turing machines 3353: 3347: 3344: 3337:needs expansion 3322: 3313:Halting problem 3300: 3295: 3286: 3280: 3276: 3272: 3268: 3264: 3215: 3212: 3211: 3207: 3179: 3176: 3175: 3129: 3126: 3125: 3121: 3037: 3032: 3016: 3011: 2992: 2987: 2948: 2945: 2944: 2936: 2932: 2928: 2905: 2900: 2884: 2879: 2860: 2855: 2807: 2804: 2803: 2780: 2776: 2762: 2759: 2758: 2754: 2750: 2730: 2702: 2698: 2683: 2679: 2661: 2657: 2642: 2638: 2630: 2627: 2626: 2599: 2596: 2595: 2591:strong equality 2578: 2549: 2545: 2530: 2526: 2521: 2518: 2517: 2492: 2489: 2488: 2484: 2462: 2461: 2450: 2441: 2437: 2422: 2418: 2403: 2402: 2397: 2363: 2352: 2343: 2339: 2324: 2320: 2290: 2289: 2282: 2280: 2279: 2264: 2260: 2245: 2241: 2222: 2220: 2217: 2216: 2211:is defined by: 2187: 2184: 2183: 2158: 2154: 2139: 2135: 2121: 2118: 2117: 2109: 2078: 2075: 2074: 2054: 2050: 2035: 2031: 2019: 2015: 2000: 1996: 1970: 1967: 1966: 1946: 1942: 1927: 1923: 1915: 1912: 1911: 1891: 1887: 1872: 1868: 1854: 1851: 1850: 1832: 1831: 1818: 1814: 1799: 1795: 1783: 1779: 1764: 1760: 1729: 1720: 1716: 1701: 1697: 1673: 1672: 1663: 1659: 1644: 1640: 1627: 1618: 1614: 1599: 1595: 1580: 1579: 1574: 1566: 1544: 1543: 1538: 1536: 1535: 1530: 1508: 1506: 1503: 1502: 1477: 1473: 1458: 1454: 1434: 1431: 1430: 1405: 1401: 1386: 1382: 1374: 1371: 1370: 1362: 1332: 1328: 1313: 1309: 1300: 1296: 1278: 1274: 1259: 1255: 1246: 1242: 1234: 1231: 1230: 1207: 1203: 1188: 1184: 1175: 1171: 1153: 1149: 1134: 1130: 1121: 1117: 1115: 1112: 1111: 1091: 1087: 1072: 1068: 1060: 1057: 1056: 1026: 1022: 1007: 1003: 994: 990: 972: 968: 953: 949: 940: 936: 918: 914: 899: 895: 883: 858: 857: 852: 850: 849: 837: 833: 818: 814: 803: 800: 799: 775: 771: 756: 752: 743: 739: 721: 717: 702: 698: 689: 685: 683: 680: 679: 658: 654: 639: 635: 627: 624: 623: 602: 599: 598: 587:Operators (the 560: 556: 538: 537: 532: 530: 529: 517: 513: 498: 494: 485: 480: 474: 471: 470: 438: 435: 434: 412: 409: 408: 387: 382: 376: 373: 372: 325: 324: 319: 317: 316: 299: 296: 295: 244: 243: 238: 236: 235: 223: 219: 204: 200: 191: 186: 180: 177: 176: 169: 165: 159: 156: 155: 154: 152: 128: 115: 98: 84:lambda calculus 65:Turing machines 45:natural numbers 17: 12: 11: 5: 4967: 4957: 4956: 4951: 4937: 4936: 4931: 4924: 4923:External links 4921: 4919: 4918: 4912: 4888:Boolos, George 4883: 4882: 4874: 4873: 4867: 4851: 4845: 4830: 4824: 4807: 4804: 4803: 4791: 4755: 4735: 4726: 4714: 4702: 4690: 4671: 4648: 4645: 4642: 4639: 4636: 4633: 4627: 4596: 4573: 4567: 4516: 4510: 4479: 4469: 4446: 4443: 4440: 4437: 4431: 4400: 4365:(4): 153–163. 4344: 4333:(2): 340–352. 4308: 4302:, Sect.1.7: " 4288: 4269: 4268: 4266: 4263: 4262: 4261: 4256: 4251: 4244: 4241: 4240: 4239: 4234: 4227: 4224: 4223: 4222: 4221: 4220: 4208: 4207: 4206: 4205: 4201: 4200: 4194: 4188: 4182: 4176: 4170: 4164: 4158: 4152: 4140: 4139: 4138: 4137: 4136: 4135: 4129: 4123: 4117: 4110: 4109: 4103: 4097: 4091: 4079: 4078: 4077: 4076: 4061: 4047: 4046: 4031: 4030: 4029: 4028: 4013: 4012: 4011: 4010: 4006: 4002: 3996: 3975: 3967: 3959: 3958: 3954: 3950: 3940: 3927: 3926: 3920: 3911: 3905: 3902: 3892: 3879: 3872: 3871: 3867: 3863: 3857: 3850: 3844: 3834: 3833: 3832: 3831: 3827: 3823: 3819: 3813: 3812: 3805: 3804: 3803: 3802: 3798: 3795: 3789: 3780: 3779: 3771: 3761: 3743: 3739: 3734: 3731: 3704: 3671: 3670: 3658: 3655: 3650: 3646: 3642: 3639: 3636: 3631: 3627: 3623: 3620: 3617: 3614: 3611: 3608: 3605: 3602: 3599: 3596: 3593: 3588: 3584: 3580: 3577: 3574: 3569: 3565: 3561: 3558: 3526: 3521: 3517: 3513: 3510: 3507: 3502: 3498: 3494: 3491: 3470: 3465: 3461: 3457: 3454: 3451: 3446: 3442: 3438: 3435: 3432: 3429: 3426: 3423: 3402: 3399: 3396: 3393: 3373: 3370: 3355: 3354: 3334: 3332: 3321: 3318: 3299: 3296: 3294: 3293: 3290: 3285: 3284: 3249: 3246: 3243: 3240: 3237: 3234: 3231: 3228: 3225: 3222: 3219: 3195: 3192: 3189: 3186: 3183: 3163: 3160: 3157: 3154: 3151: 3148: 3145: 3142: 3139: 3136: 3133: 3109: 3106: 3103: 3100: 3097: 3094: 3091: 3088: 3085: 3082: 3079: 3076: 3073: 3070: 3067: 3064: 3061: 3058: 3055: 3052: 3048: 3045: 3040: 3035: 3031: 3027: 3024: 3019: 3014: 3010: 3006: 3003: 3000: 2995: 2990: 2986: 2982: 2979: 2976: 2973: 2970: 2967: 2964: 2961: 2958: 2955: 2952: 2916: 2913: 2908: 2903: 2899: 2895: 2892: 2887: 2882: 2878: 2874: 2871: 2868: 2863: 2858: 2854: 2850: 2847: 2844: 2841: 2838: 2835: 2832: 2829: 2826: 2823: 2820: 2817: 2814: 2811: 2791: 2788: 2783: 2779: 2775: 2772: 2769: 2766: 2742: 2729: 2726: 2722: 2721: 2710: 2705: 2701: 2697: 2694: 2691: 2686: 2682: 2678: 2675: 2672: 2669: 2664: 2660: 2656: 2653: 2650: 2645: 2641: 2637: 2634: 2603: 2560: 2557: 2552: 2548: 2544: 2541: 2538: 2533: 2529: 2525: 2505: 2502: 2499: 2496: 2480: 2479: 2478: 2477: 2476: 2475: 2459: 2456: 2453: 2451: 2449: 2444: 2440: 2436: 2433: 2430: 2425: 2421: 2417: 2414: 2411: 2408: 2405: 2404: 2395: 2392: 2389: 2386: 2383: 2380: 2377: 2374: 2371: 2361: 2358: 2355: 2353: 2351: 2346: 2342: 2338: 2335: 2332: 2327: 2323: 2319: 2316: 2313: 2310: 2299: 2296: 2293: 2286: 2278: 2275: 2272: 2267: 2263: 2259: 2256: 2253: 2248: 2244: 2240: 2237: 2234: 2231: 2228: 2225: 2224: 2200: 2197: 2194: 2191: 2182:-ary function 2166: 2161: 2157: 2153: 2150: 2147: 2142: 2138: 2134: 2131: 2128: 2125: 2104: 2103: 2102: 2091: 2088: 2085: 2082: 2062: 2057: 2053: 2049: 2046: 2043: 2038: 2034: 2030: 2027: 2022: 2018: 2014: 2011: 2008: 2003: 1999: 1995: 1992: 1989: 1986: 1983: 1980: 1977: 1974: 1954: 1949: 1945: 1941: 1938: 1935: 1930: 1926: 1922: 1919: 1899: 1894: 1890: 1886: 1883: 1880: 1875: 1871: 1867: 1864: 1861: 1858: 1847: 1846: 1845: 1830: 1826: 1821: 1817: 1813: 1810: 1807: 1802: 1798: 1794: 1791: 1786: 1782: 1778: 1775: 1772: 1767: 1763: 1759: 1756: 1753: 1750: 1747: 1744: 1741: 1738: 1735: 1732: 1730: 1728: 1723: 1719: 1715: 1712: 1709: 1704: 1700: 1696: 1693: 1690: 1687: 1684: 1681: 1678: 1675: 1674: 1671: 1666: 1662: 1658: 1655: 1652: 1647: 1643: 1639: 1636: 1633: 1630: 1628: 1626: 1621: 1617: 1613: 1610: 1607: 1602: 1598: 1594: 1591: 1588: 1585: 1582: 1581: 1573: 1564: 1553: 1550: 1547: 1541: 1531: 1529: 1526: 1523: 1520: 1517: 1514: 1511: 1510: 1485: 1480: 1476: 1472: 1469: 1466: 1461: 1457: 1453: 1450: 1447: 1444: 1441: 1438: 1413: 1408: 1404: 1400: 1397: 1394: 1389: 1385: 1381: 1378: 1369:-ary function 1357: 1356: 1355: 1343: 1340: 1335: 1331: 1327: 1324: 1321: 1316: 1312: 1308: 1303: 1299: 1295: 1292: 1289: 1286: 1281: 1277: 1273: 1270: 1267: 1262: 1258: 1254: 1249: 1245: 1241: 1238: 1218: 1215: 1210: 1206: 1202: 1199: 1196: 1191: 1187: 1183: 1178: 1174: 1170: 1167: 1164: 1161: 1156: 1152: 1148: 1145: 1142: 1137: 1133: 1129: 1124: 1120: 1099: 1094: 1090: 1086: 1083: 1080: 1075: 1071: 1067: 1064: 1053: 1052: 1051: 1040: 1037: 1034: 1029: 1025: 1021: 1018: 1015: 1010: 1006: 1002: 997: 993: 989: 986: 983: 980: 975: 971: 967: 964: 961: 956: 952: 948: 943: 939: 935: 932: 929: 926: 921: 917: 913: 910: 907: 902: 898: 894: 891: 881: 878: 867: 864: 861: 855: 845: 840: 836: 832: 829: 826: 821: 817: 813: 810: 807: 783: 778: 774: 770: 767: 764: 759: 755: 751: 746: 742: 738: 735: 732: 729: 724: 720: 716: 713: 710: 705: 701: 697: 692: 688: 666: 661: 657: 653: 650: 647: 642: 638: 634: 631: 606: 585: 584: 583: 582: 581: 580: 569: 563: 559: 547: 544: 541: 535: 525: 520: 516: 512: 509: 506: 501: 497: 493: 488: 483: 479: 454: 451: 448: 445: 442: 422: 419: 416: 390: 385: 381: 367: 366: 365: 364: 363: 351: 348: 345: 334: 331: 328: 322: 312: 309: 306: 303: 286: 285: 284: 277: 276: 275: 264: 253: 250: 247: 241: 231: 226: 222: 218: 215: 212: 207: 203: 199: 194: 189: 185: 157: 114: 111: 15: 9: 6: 4: 3: 2: 4966: 4955: 4952: 4950: 4947: 4946: 4944: 4935: 4932: 4930: 4927: 4926: 4915: 4913:9780521007580 4909: 4905: 4901: 4897: 4893: 4892:Burgess, John 4889: 4885: 4884: 4880: 4876: 4875: 4870: 4868:9780131654495 4864: 4860: 4856: 4852: 4848: 4846:9783540152996 4842: 4838: 4837: 4831: 4827: 4825:0-7204-2103-9 4821: 4817: 4813: 4809: 4808: 4800: 4795: 4786: 4781: 4777: 4773: 4766: 4759: 4753: 4749: 4745: 4739: 4730: 4721: 4719: 4709: 4707: 4697: 4695: 4669: 4646: 4643: 4640: 4637: 4634: 4631: 4594: 4571: 4514: 4477: 4467: 4444: 4441: 4438: 4435: 4398: 4388: 4384: 4380: 4376: 4372: 4368: 4364: 4360: 4359: 4354: 4348: 4340: 4336: 4332: 4328: 4327: 4322: 4318: 4312: 4305: 4301: 4297: 4292: 4284: 4280: 4274: 4270: 4260: 4257: 4255: 4252: 4250: 4247: 4246: 4238: 4235: 4233: 4230: 4229: 4219: 4215: 4214: 4213: 4212: 4211: 4203: 4202: 4189: 4177: 4165: 4153: 4150: 4149: 4148: 4147: 4146: 4144: 4124: 4112: 4111: 4098: 4086: 4085: 4084: 4083: 4081: 4080: 4074: 4070: 4066: 4062: 4059: 4055: 4051: 4050: 4049: 4048: 4044: 4040: 4036: 4033: 4032: 4026: 4022: 4018: 4017: 4015: 4014: 3992: 3988: 3984: 3983: 3981: 3973: 3965: 3961: 3960: 3948: 3936: 3932: 3929: 3928: 3906: 3900: 3887: 3874: 3873: 3839: 3836: 3835: 3822:a', where 1 = 3818:S(a) = a +1 = 3817: 3816: 3815: 3814: 3810: 3807: 3806: 3796: 3784: 3783: 3782: 3781: 3777: 3769: 3756: 3753: 3752: 3751: 3749: 3729: 3727: 3720: 3718: 3702: 3695:observes the 3694: 3690: 3688: 3684: 3680: 3677:is called an 3676: 3648: 3644: 3640: 3637: 3634: 3629: 3625: 3621: 3618: 3609: 3603: 3597: 3594: 3586: 3582: 3578: 3575: 3572: 3567: 3563: 3556: 3549: 3548: 3547: 3545: 3541: 3519: 3515: 3511: 3508: 3505: 3500: 3496: 3489: 3463: 3459: 3455: 3452: 3449: 3444: 3440: 3436: 3433: 3430: 3427: 3421: 3397: 3391: 3383: 3379: 3369: 3366: 3362: 3351: 3348:February 2010 3342: 3338: 3335:This section 3333: 3330: 3326: 3325: 3317: 3315: 3314: 3309: 3305: 3292: 3291: 3289: 3263: 3247: 3244: 3238: 3232: 3229: 3223: 3217: 3206:is the least 3190: 3184: 3181: 3174:holds. Hence 3161: 3158: 3152: 3146: 3143: 3137: 3131: 3104: 3101: 3095: 3089: 3086: 3080: 3074: 3065: 3059: 3056: 3053: 3038: 3033: 3029: 3025: 3017: 3012: 3008: 3004: 3001: 2998: 2993: 2988: 2984: 2980: 2977: 2971: 2968: 2962: 2959: 2956: 2953: 2942: 2906: 2901: 2897: 2893: 2885: 2880: 2876: 2872: 2869: 2866: 2861: 2856: 2852: 2848: 2845: 2839: 2836: 2830: 2827: 2824: 2821: 2815: 2812: 2809: 2789: 2786: 2781: 2773: 2770: 2767: 2748: 2744: 2743: 2741: 2737: 2735: 2725: 2703: 2699: 2695: 2692: 2689: 2684: 2680: 2673: 2670: 2662: 2658: 2654: 2651: 2648: 2643: 2639: 2632: 2625: 2624: 2623: 2621: 2617: 2601: 2593: 2592: 2586: 2584: 2576: 2571: 2558: 2550: 2546: 2542: 2539: 2536: 2531: 2527: 2500: 2494: 2457: 2454: 2452: 2442: 2438: 2434: 2431: 2428: 2423: 2419: 2415: 2412: 2406: 2393: 2390: 2387: 2384: 2381: 2378: 2375: 2372: 2369: 2359: 2356: 2354: 2344: 2340: 2336: 2333: 2330: 2325: 2321: 2317: 2314: 2308: 2276: 2273: 2265: 2261: 2257: 2254: 2251: 2246: 2242: 2232: 2226: 2215: 2214: 2213: 2212: 2195: 2189: 2181: 2159: 2155: 2151: 2148: 2145: 2140: 2136: 2132: 2129: 2123: 2115: 2108: 2105: 2089: 2086: 2083: 2080: 2055: 2051: 2047: 2044: 2041: 2036: 2032: 2028: 2020: 2016: 2012: 2009: 2006: 2001: 1997: 1993: 1990: 1984: 1981: 1978: 1972: 1947: 1943: 1939: 1936: 1933: 1928: 1924: 1917: 1892: 1888: 1884: 1881: 1878: 1873: 1869: 1865: 1862: 1856: 1848: 1828: 1819: 1815: 1811: 1808: 1805: 1800: 1796: 1792: 1784: 1780: 1776: 1773: 1770: 1765: 1761: 1757: 1754: 1748: 1745: 1742: 1736: 1733: 1731: 1721: 1717: 1713: 1710: 1707: 1702: 1698: 1694: 1688: 1682: 1676: 1664: 1660: 1656: 1653: 1650: 1645: 1641: 1634: 1631: 1629: 1619: 1615: 1611: 1608: 1605: 1600: 1596: 1592: 1589: 1583: 1571: 1562: 1539: 1524: 1521: 1518: 1512: 1501: 1500: 1499: 1498: 1478: 1474: 1470: 1467: 1464: 1459: 1455: 1451: 1448: 1445: 1442: 1436: 1428: 1406: 1402: 1398: 1395: 1392: 1387: 1383: 1376: 1368: 1361: 1358: 1333: 1329: 1325: 1322: 1319: 1314: 1310: 1301: 1297: 1293: 1290: 1287: 1279: 1275: 1271: 1268: 1265: 1260: 1256: 1247: 1243: 1236: 1216: 1208: 1204: 1200: 1197: 1194: 1189: 1185: 1176: 1172: 1168: 1165: 1162: 1154: 1150: 1146: 1143: 1140: 1135: 1131: 1122: 1118: 1092: 1088: 1084: 1081: 1078: 1073: 1069: 1062: 1054: 1038: 1027: 1023: 1019: 1016: 1013: 1008: 1004: 995: 991: 987: 984: 981: 973: 969: 965: 962: 959: 954: 950: 941: 937: 930: 927: 919: 915: 911: 908: 905: 900: 896: 889: 879: 876: 853: 838: 834: 830: 827: 824: 819: 815: 808: 805: 798: 797: 796: 795: 776: 772: 768: 765: 762: 757: 753: 744: 740: 736: 733: 730: 722: 718: 714: 711: 708: 703: 699: 690: 686: 659: 655: 651: 648: 645: 640: 636: 629: 621: 604: 597: 594: 593: 592: 590: 567: 561: 557: 533: 518: 514: 510: 507: 504: 499: 495: 486: 481: 477: 469: 468: 467: 466: 452: 449: 446: 443: 440: 420: 417: 414: 406: 388: 383: 379: 371: 368: 349: 346: 343: 320: 307: 301: 294: 293: 292: 291: 290: 287: 282: 281:zero function 278: 262: 239: 224: 220: 216: 213: 210: 205: 201: 192: 187: 183: 175: 174: 173: 172: 163: 149: 148: 147: 144: 142: 138: 133: 131: 124: 120: 110: 108: 104: 96: 91: 89: 85: 80: 78: 74: 70: 66: 62: 58: 54: 50: 46: 42: 38: 34: 30: 26: 22: 4903: 4858: 4835: 4815: 4794: 4778:(1): 41–73. 4775: 4771: 4758: 4738: 4729: 4362: 4356: 4347: 4330: 4324: 4311: 4303: 4291: 4282: 4273: 4217: 4209: 4142: 4141: 4108:( b, c, a )) 4072: 4068: 4064: 4057: 4053: 4042: 4038: 4034: 4024: 4020: 3990: 3986: 3979: 3971: 3963: 3946: 3934: 3930: 3898: 3885: 3837: 3808: 3775: 3767: 3754: 3747: 3736: 3725: 3722: 3691: 3686: 3683:Gödel number 3682: 3678: 3674: 3672: 3543: 3539: 3381: 3375: 3358: 3345: 3341:adding to it 3336: 3311: 3303: 3301: 3287: 2738: 2731: 2723: 2619: 2615: 2589: 2587: 2574: 2572: 2481: 2179: 2113: 2106: 1426: 1366: 1365:: Given the 1359: 619: 595: 586: 404: 369: 288: 280: 150: 145: 134: 122: 118: 116: 101:is known in 94: 92: 81: 56: 52: 36: 32: 28: 18: 4799:Minsky 1972 4742:defined in 3830:0 ' ', etc. 3673:The number 2112:: Given a ( 4943:Categories 4675:-definable 4600:-recursive 4483:-definable 4404:-definable 4265:References 4045:)". Given: 3974:), ... , f 3797:e.g. const 3546:such that 3279:seeks for 3210:such that 2757:such that 2577:functions 433:such that 168:and every 113:Definition 49:formal one 4857:(1972) . 4814:(1991) . 4670:λ 4626:⟹ 4595:μ 4566:⟹ 4509:⟹ 4468:λ 4430:⟹ 4399:λ 4254:Recursion 4151:S(a) = a' 4122:(a), S } 4005:, ... , f 3733:Symbolism 3638:… 3604:μ 3595:≃ 3576:… 3509:… 3453:… 3230:∗ 3185:⁡ 3144:∗ 3087:∗ 3072:¬ 3005:∘ 2981:∘ 2972:∘ 2963:∘ 2957:∘ 2873:∘ 2849:∘ 2840:∘ 2831:∘ 2825:∘ 2816:μ 2693:… 2671:≃ 2652:… 2602:≃ 2594:relation 2540:… 2495:μ 2432:… 2391:− 2382:… 2334:… 2285:⟺ 2255:… 2227:μ 2190:μ 2149:… 2045:… 2010:… 1937:… 1882:… 1809:… 1774:… 1711:… 1654:… 1609:… 1513:ρ 1468:… 1396:… 1323:… 1291:… 1269:… 1198:… 1166:… 1144:… 1082:… 1017:… 985:… 963:… 909:… 828:… 809:∘ 766:… 734:… 712:… 649:… 605:∘ 508:… 450:≤ 444:≤ 214:… 4898:(2002). 4319:(1936). 4298:, Entry 4243:See also 4226:Examples 4134:(a), S } 3778:) = n ": 3742:, ..., x 3275:, while 2927:, where 2728:Examples 2622:so that 4387:2317046 4379:2268280 4163:(a) = a 4143:Example 3966:)= g( f 3826:0', 2 = 3359:In the 3262:junctor 105:as the 4910:  4865:  4843:  4822:  4750:, and 4385:  4377:  4216:a+b = 4060:), and 4056:)= f( 4023:)= Cn( 3907:e.g. U 3888:) = id 3785:e.g. C 3693:Minsky 3277:μ 2935:, and 2306:  2178:, the 2110:μ 1560:  1533:  1363:ρ 874:  847:  554:  527:  341:  314:  260:  233:  59:). In 4768:(PDF) 4383:S2CID 4375:JSTOR 4125:Pr{ U 4113:R { U 4001:(g, f 3901:) = x 3679:index 3538:with 3182:Isqrt 2810:Isqrt 2583:below 2575:total 885:where 99:{0,1} 95:total 43:from 39:is a 35:, or 4908:ISBN 4863:ISBN 4841:ISBN 4820:ISBN 3989:) = 3982:) ) 3916:= id 3866:to x 3414:and 3245:> 3159:> 3102:> 2939:are 2787:> 2745:The 2618:and 2588:The 2357:> 2084:< 1965:and 1425:and 1229:and 121:(or 117:The 27:, a 23:and 4780:doi 4572:161 4515:160 4367:doi 4335:doi 4199:(a) 4096:(a) 3828:def 3824:def 3820:def 3681:or 3343:. 3265:Not 3120:is 2969:Mul 2954:Not 2937:Mul 2929:Not 2837:Mul 2822:Not 2749:of 2399:and 2365:for 19:In 4945:: 4902:. 4894:; 4890:; 4776:53 4774:. 4770:. 4746:, 4717:^ 4705:^ 4693:^ 4381:. 4373:. 4361:. 4329:. 4323:. 4281:. 4071:), 4021:x' 4019:h( 3985:h( 3957:": 3897:( 3884:( 3799:13 3790:13 3774:( 3750:: 3719:: 3376:A 3316:. 3269:Gt 2960:Gt 2933:Gt 2931:, 2828:Gt 2736:. 1497:: 794:: 465:: 132:. 109:. 90:. 79:. 31:, 4916:. 4871:. 4849:. 4828:. 4788:. 4782:: 4647:e 4644:n 4641:e 4638:e 4635:l 4632:K 4478:K 4473:- 4445:v 4442:i 4439:r 4436:t 4389:. 4369:: 4363:2 4341:. 4337:: 4331:2 4306:" 4218:R 4195:1 4183:2 4171:2 4166:U 4159:1 4154:U 4130:1 4118:1 4104:2 4092:1 4075:) 4073:x 4069:x 4065:x 4058:x 4054:x 4043:x 4039:R 4027:) 4025:x 4009:) 4007:m 4003:1 3997:m 3991:S 3987:x 3980:x 3978:( 3976:m 3972:x 3970:( 3968:1 3964:x 3955:n 3951:m 3947:! 3941:n 3935:S 3921:3 3912:3 3903:i 3899:x 3893:i 3886:x 3880:i 3875:U 3870:: 3868:n 3864:1 3858:i 3851:i 3845:i 3776:x 3772:n 3768:x 3766:( 3762:q 3748:x 3744:n 3740:1 3738:x 3703:U 3687:f 3675:e 3669:. 3657:) 3654:) 3649:k 3645:x 3641:, 3635:, 3630:1 3626:x 3622:, 3619:e 3616:( 3613:) 3610:T 3607:( 3601:( 3598:U 3592:) 3587:k 3583:x 3579:, 3573:, 3568:1 3564:x 3560:( 3557:f 3544:e 3540:k 3525:) 3520:k 3516:x 3512:, 3506:, 3501:1 3497:x 3493:( 3490:f 3469:) 3464:k 3460:x 3456:, 3450:, 3445:1 3441:x 3437:, 3434:e 3431:, 3428:y 3425:( 3422:T 3401:) 3398:y 3395:( 3392:U 3382:k 3350:) 3346:( 3283:. 3281:0 3273:1 3248:x 3242:) 3239:z 3236:( 3233:S 3227:) 3224:z 3221:( 3218:S 3208:z 3194:) 3191:x 3188:( 3162:x 3156:) 3153:z 3150:( 3147:S 3141:) 3138:z 3135:( 3132:S 3122:0 3108:) 3105:x 3099:) 3096:z 3093:( 3090:S 3084:) 3081:z 3078:( 3075:S 3069:( 3066:= 3063:) 3060:x 3057:, 3054:z 3051:( 3047:) 3044:) 3039:2 3034:2 3030:P 3026:, 3023:) 3018:2 3013:1 3009:P 3002:S 2999:, 2994:2 2989:1 2985:P 2978:S 2975:( 2966:( 2951:( 2915:) 2912:) 2907:2 2902:2 2898:P 2894:, 2891:) 2886:2 2881:1 2877:P 2870:S 2867:, 2862:2 2857:1 2853:P 2846:S 2843:( 2834:( 2819:( 2813:= 2790:x 2782:2 2778:) 2774:1 2771:+ 2768:z 2765:( 2755:z 2751:x 2709:) 2704:l 2700:x 2696:, 2690:, 2685:1 2681:x 2677:( 2674:g 2668:) 2663:k 2659:x 2655:, 2649:, 2644:1 2640:x 2636:( 2633:f 2620:g 2616:f 2579:f 2559:. 2556:) 2551:k 2547:x 2543:, 2537:, 2532:1 2528:x 2524:( 2504:) 2501:f 2498:( 2485:f 2458:0 2455:= 2448:) 2443:k 2439:x 2435:, 2429:, 2424:1 2420:x 2416:, 2413:z 2410:( 2407:f 2394:1 2388:z 2385:, 2379:, 2376:0 2373:= 2370:i 2360:0 2350:) 2345:k 2341:x 2337:, 2331:, 2326:1 2322:x 2318:, 2315:i 2312:( 2309:f 2298:f 2295:e 2292:d 2277:z 2274:= 2271:) 2266:k 2262:x 2258:, 2252:, 2247:1 2243:x 2239:( 2236:) 2233:f 2230:( 2199:) 2196:f 2193:( 2180:k 2165:) 2160:k 2156:x 2152:, 2146:, 2141:1 2137:x 2133:, 2130:y 2127:( 2124:f 2114:k 2090:. 2087:y 2081:z 2061:) 2056:k 2052:x 2048:, 2042:, 2037:1 2033:x 2029:, 2026:) 2021:k 2017:x 2013:, 2007:, 2002:1 1998:x 1994:, 1991:z 1988:( 1985:f 1982:, 1979:z 1976:( 1973:h 1953:) 1948:k 1944:x 1940:, 1934:, 1929:1 1925:x 1921:( 1918:g 1898:) 1893:k 1889:x 1885:, 1879:, 1874:1 1870:x 1866:, 1863:y 1860:( 1857:f 1829:. 1825:) 1820:k 1816:x 1812:, 1806:, 1801:1 1797:x 1793:, 1790:) 1785:k 1781:x 1777:, 1771:, 1766:1 1762:x 1758:, 1755:y 1752:( 1749:f 1746:, 1743:y 1740:( 1737:h 1734:= 1727:) 1722:k 1718:x 1714:, 1708:, 1703:1 1699:x 1695:, 1692:) 1689:y 1686:( 1683:S 1680:( 1677:f 1670:) 1665:k 1661:x 1657:, 1651:, 1646:1 1642:x 1638:( 1635:g 1632:= 1625:) 1620:k 1616:x 1612:, 1606:, 1601:1 1597:x 1593:, 1590:0 1587:( 1584:f 1572:f 1563:f 1552:f 1549:e 1546:d 1540:= 1528:) 1525:h 1522:, 1519:g 1516:( 1484:) 1479:k 1475:x 1471:, 1465:, 1460:1 1456:x 1452:, 1449:z 1446:, 1443:y 1440:( 1437:h 1427:k 1412:) 1407:k 1403:x 1399:, 1393:, 1388:1 1384:x 1380:( 1377:g 1367:k 1342:) 1339:) 1334:k 1330:x 1326:, 1320:, 1315:1 1311:x 1307:( 1302:m 1298:g 1294:, 1288:, 1285:) 1280:k 1276:x 1272:, 1266:, 1261:1 1257:x 1253:( 1248:1 1244:g 1240:( 1237:h 1217:, 1214:) 1209:k 1205:x 1201:, 1195:, 1190:1 1186:x 1182:( 1177:m 1173:g 1169:, 1163:, 1160:) 1155:k 1151:x 1147:, 1141:, 1136:1 1132:x 1128:( 1123:1 1119:g 1098:) 1093:k 1089:x 1085:, 1079:, 1074:1 1070:x 1066:( 1063:f 1039:. 1036:) 1033:) 1028:k 1024:x 1020:, 1014:, 1009:1 1005:x 1001:( 996:m 992:g 988:, 982:, 979:) 974:k 970:x 966:, 960:, 955:1 951:x 947:( 942:1 938:g 934:( 931:h 928:= 925:) 920:k 916:x 912:, 906:, 901:1 897:x 893:( 890:f 880:, 877:f 866:f 863:e 860:d 854:= 844:) 839:m 835:g 831:, 825:, 820:1 816:g 812:( 806:h 782:) 777:k 773:x 769:, 763:, 758:1 754:x 750:( 745:m 741:g 737:, 731:, 728:) 723:k 719:x 715:, 709:, 704:1 700:x 696:( 691:1 687:g 665:) 660:m 656:x 652:, 646:, 641:1 637:x 633:( 630:h 568:. 562:i 558:x 546:f 543:e 540:d 534:= 524:) 519:k 515:x 511:, 505:, 500:1 496:x 492:( 487:k 482:i 478:P 453:k 447:i 441:1 421:k 418:, 415:i 389:k 384:i 380:P 350:1 347:+ 344:x 333:f 330:e 327:d 321:= 311:) 308:x 305:( 302:S 263:n 252:f 249:e 246:d 240:= 230:) 225:k 221:x 217:, 211:, 206:1 202:x 198:( 193:k 188:n 184:C 170:k 166:n 158:n 153:C 129:μ

Index

mathematical logic
computer science
partial function
natural numbers
formal one
computability theory
Turing machines
Church–Turing thesis
primitive recursive functions
Ackermann function
lambda calculus
Markov algorithms
computational complexity theory
complexity class R
minimization operator μ
primitive recursive functions
Ackermann function
domain of a function
below
strong equality
Primitive recursive function#Examples
integer square root
logical negation
junctor
total Turing machine
Halting problem

adding to it
equivalence of models of computability
Turing machines

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