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Inductive type

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started as a study into the limits of ITT. Once found, the limits were turned into rules that allowed defining new inductive types. These types could depend upon a function and the function on the type, as long as both were defined simultaneously.
1977:(HoTT). HoTT differs from ITT by its identity type (equality). Higher inductive types not only define a new type with constants and functions that create elements of the type, but also new instances of the identity type that relate them. 727: 722: 354:
In words: for any predicate "P" over natural numbers, given a proof of "P 0" and a proof of "P n -> P (n+1)", we get back a proof of "forall n, P n". This is the familiar induction principle for natural numbers.
590: 994: 1146: 892: 1664:{\displaystyle {\frac {w:{\mathsf {W}}_{a:A}B(a)\qquad a:A,\;f:B(a)\to {\mathsf {W}}_{x:A}B(x),\;c:\prod _{b:B(a)}C(f(b))\;\vdash \;h(a,f,c):C({\mathsf {sup}}(a,f))}{{\mathsf {elim}}(w,h):C(w)}}} 732: 1366: 933: 989: 454: 2377: 1963: 1685:. In this case, the property of initiality (res. finality) corresponds directly to the appropriate induction principle. In intensional type theories with the 2372: 827:{\displaystyle {\begin{aligned}f(\operatorname {inl} (1_{\mathbf {1} }))&=\mathbf {0} \\f(\operatorname {inr} (a))&=\mathbf {1} \end{aligned}}} 646: 536: 468:
of each constructor. W-types (resp. M-types) may also be understood as well-founded (resp. non-well-founded) trees with nodes labeled by elements
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if it has facilities for creating a new type from constants and functions that create terms of that type. The feature serves a role similar to
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Here, a natural number is created either from the constant "0" or by applying the function "S" to another natural number. "S" is the
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may be thought of as "labels" for the (potentially infinitely many) constructors of the inductive type being defined, whereas
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which represents adding 1 to a number. Thus, "0" is zero, "S 0" is one, "S (S 0)" is two, "S (S (S 0))" is three, and so on.
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Inductive types usually come with a function to prove properties about them. Thus, "nat" may come with (in Coq syntax):
1132:{\displaystyle {\mathsf {sup}}:\prod _{a:A}{\Big (}B(a)\to {\mathsf {W}}_{x:A}B(x){\Big )}\to {\mathsf {W}}_{x:A}B(x).} 72: 1310: 1290:{\displaystyle {\frac {a:A\qquad f:B(a)\to {\mathsf {W}}_{x:A}B(x)}{{\mathsf {sup}}(a,f):{\mathsf {W}}_{x:A}B(x)}}.} 373: 230:
Since their introduction, inductive types have been extended to encode more and more structures, while still being
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Awodey, Steve; Gambino, Nicola; Sojakova, Kristina (2015-04-21). "Homotopy-initial algebras in type theory".
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Awodey, Steve; Gambino, Nicola; Sojakova, Kristina (2012-01-18). "Inductive types in homotopy type theory".
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Dybjer, Peter (1997). "Representing inductively defined sets by wellorderings in Martin-Löf's type theory".
61: 2326: 1906: 1693: 381: 142: 149:. As the name suggests, inductive types can be self-referential, but usually only in a way that permits 369: 2056: 2397: 1974: 1717: 1300: 376:(ITT). They generalize natural numbers, lists, binary trees, and other "tree-shaped" data types. Let 150: 1917: 146: 2331: 2295: 2277: 2248: 2229: 2199: 2174: 2128: 2098: 1927: 1368:
holds for all subtrees of a given tree it also holds for that tree, then it holds for all trees.
224: 2219: 2118: 2075: 2065: 1140: 2336: 2287: 2209: 2155: 2108: 1686: 86: 2198:. Leibniz International Proceedings in Informatics (LIPIcs). Vol. 38. pp. 17–30. 2097:. Leibniz International Proceedings in Informatics (LIPIcs). Vol. 38. pp. 17–30. 1678: 2268:
van den Berg, Benno; Marchi, Federico De (2007). "Non-well-founded trees in categories".
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definitions of multiple types that depend on each other. For example, defining two
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allows definition of a type and a family of types at the same time. So, a type
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In extensional type theories, W-types (resp. M-types) can be defined up to
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corresponds to the constructor for the empty list, whereas the value of
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in a programming language and allows a type theory to add concepts like
618:(representing the constructor for zero, which takes no arguments), and 2356: 2282: 1689:, this correspondence holds up to homotopy (propositional equality). 138: 2253: 2204: 2103: 2194:
Ahrens, Benedikt; Capriotti, Paolo; Spadotti, Régis (2015-04-12).
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Ahrens, Benedikt; Capriotti, Paolo; Spadotti, Régis (2015-04-12).
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The existence of a new constructor for the identity type makes
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Abbott, Michael; Altenkirch, Thorsten; Ghani, Neil (2005).
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type, which is defined with two constructors, a basepoint;
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Homotopy Type Theory: Univalent Foundations of Mathematics
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permits (effectively) infinite structures in type theory.
887:{\displaystyle f(\operatorname {inl} (1_{\mathbf {1} }))} 533:, etc. One may define the natural numbers as the W-type 1930: 1376: 1313: 1149: 997: 948: 900: 850: 730: 649: 539: 413: 1299:
The elimination rule for W-types works similarly to
53:. Unsourced material may be challenged and removed. 2315:"Containers: Constructing strictly positive types" 1957: 1663: 1360: 1289: 1131: 983: 927: 886: 826: 716: 584: 448: 1086: 1032: 942:The constructor for elements of a generic W-type 2383:Higher Inductive Types: a tour of the menagerie 1361:{\displaystyle C:{\mathsf {W}}_{x:A}B(x)\to U} 1139:We can also write this rule in the style of a 2196:Non-wellfounded trees in Homotopy Type Theory 2095:Non-wellfounded trees in Homotopy Type Theory 1303:on trees. If, whenever a property (under the 8: 935:corresponds to the constructor that appends 1909:can be defined using induction-recursion. 1545: 1541: 1488: 1431: 928:{\displaystyle f(\operatorname {inr} (a))} 2340: 2330: 2281: 2252: 2213: 2203: 2178: 2112: 2102: 2064:. Sambin, Giovanni. Napoli: Bibliopolis. 1929: 1613: 1612: 1580: 1579: 1499: 1461: 1455: 1454: 1394: 1388: 1387: 1377: 1375: 1328: 1322: 1321: 1312: 1257: 1251: 1250: 1219: 1218: 1192: 1186: 1185: 1150: 1148: 1102: 1096: 1095: 1085: 1084: 1060: 1054: 1053: 1031: 1030: 1018: 999: 998: 996: 957: 951: 950: 947: 899: 871: 870: 849: 815: 775: 755: 754: 731: 729: 686: 676: 670: 669: 648: 563: 556: 550: 549: 541: 540: 538: 507:, etc. be finite types with inhabitants 1 422: 416: 415: 412: 113:Learn how and when to remove this message 2047: 1704:. M-types can be derived from W-types. 984:{\displaystyle {\mathsf {W}}_{x:A}B(x)} 449:{\displaystyle {\mathsf {W}}_{a:A}B(a)} 2355:Univalent Foundations Program (2013). 1724:using two mutually inductive types in 1623: 1620: 1617: 1614: 1587: 1584: 1581: 1456: 1389: 1323: 1252: 1226: 1223: 1220: 1187: 1097: 1055: 1006: 1003: 1000: 952: 671: 551: 417: 464:indicates the (potentially infinite) 234:and supporting structural recursion. 156:The standard example is encoding the 7: 1700:(potentially infinite) data such as 51:adding citations to reliable sources 1973:This is a current research area in 939:to the beginning of another list. 14: 635:One may define lists over a type 2270:Annals of Pure and Applied Logic 872: 816: 776: 756: 687: 564: 27: 2361:. Institute for Advanced Study. 1418: 1162: 38:needs additional citations for 1940: 1708:Mutually inductive definitions 1655: 1649: 1640: 1628: 1607: 1604: 1592: 1576: 1567: 1549: 1538: 1535: 1529: 1523: 1515: 1509: 1482: 1476: 1450: 1447: 1441: 1415: 1409: 1352: 1349: 1343: 1278: 1272: 1243: 1231: 1213: 1207: 1181: 1178: 1172: 1123: 1117: 1091: 1081: 1075: 1049: 1046: 1040: 978: 972: 922: 919: 913: 904: 881: 878: 863: 854: 805: 802: 796: 787: 765: 762: 747: 738: 711: 705: 697: 677: 662: 656: 579: 573: 476:and where the node labeled by 443: 437: 1: 2160:10.1016/s0304-3975(96)00145-4 1681:(resp. final coalgebras) for 2319:Theoretical Computer Science 2148:Theoretical Computer Science 2215:10.4230/LIPIcs.TLCA.2015.17 2114:10.4230/LIPIcs.TLCA.2015.17 1958:{\displaystyle B:A\to Type} 1696:to W-types, they represent 2414: 2378:Induction-Induction Slides 2373:Induction-Recursion Slides 2292:10.1016/j.apal.2006.12.001 2058:Intuitionistic type theory 840:is the sole inhabitant of 374:intuitionistic type theory 15: 2342:10.1016/j.tcs.2005.06.002 2025:a higher inductive type. 2055:Martin-Löf, Per (1984). 1980:A simple example is the 1730: 407:, one can form a W-type 244: 170: 16:Not to be confused with 164:. It can be defined in 1969:Higher inductive types 1959: 1924:and a family of types 1712:This technique allows 1665: 1362: 1291: 1133: 985: 929: 888: 828: 718: 586: 450: 1960: 1666: 1363: 1305:propositions-as-types 1292: 1134: 986: 930: 889: 829: 719: 587: 451: 1975:Homotopy Type Theory 1928: 1374: 1311: 1301:structural induction 1147: 995: 946: 898: 848: 728: 647: 537: 411: 151:structural recursion 47:improve this article 1918:Induction-induction 1913:Induction-induction 1900:Induction-recursion 1895:Induction-recursion 1683:polynomial functors 18:Inductive data type 1955: 1661: 1519: 1358: 1287: 1129: 1029: 981: 925: 884: 824: 822: 714: 582: 490:polynomial functor 446: 225:successor function 1659: 1495: 1282: 1141:natural deduction 1014: 382:universe of types 123: 122: 115: 97: 2405: 2362: 2347: 2346: 2344: 2334: 2310: 2304: 2303: 2285: 2265: 2259: 2258: 2256: 2244: 2238: 2237: 2217: 2207: 2191: 2185: 2184: 2182: 2170: 2164: 2163: 2154:(1–2): 329–335. 2143: 2137: 2136: 2116: 2106: 2090: 2084: 2083: 2063: 2052: 2024: 2017: 1996: 1983: 1964: 1962: 1961: 1956: 1923: 1890: 1887: 1884: 1881: 1878: 1875: 1872: 1869: 1866: 1863: 1860: 1857: 1854: 1851: 1848: 1845: 1844:S_of_even_is_odd 1842: 1839: 1836: 1833: 1830: 1827: 1824: 1821: 1818: 1815: 1812: 1809: 1806: 1803: 1800: 1797: 1794: 1791: 1788: 1785: 1782: 1779: 1776: 1773: 1772:S_of_odd_is_even 1770: 1767: 1764: 1761: 1758: 1755: 1752: 1749: 1746: 1743: 1740: 1737: 1734: 1687:univalence axiom 1679:initial algebras 1670: 1668: 1667: 1662: 1660: 1658: 1627: 1626: 1610: 1591: 1590: 1518: 1472: 1471: 1460: 1459: 1405: 1404: 1393: 1392: 1378: 1367: 1365: 1364: 1359: 1339: 1338: 1327: 1326: 1307:interpretation) 1296: 1294: 1293: 1288: 1283: 1281: 1268: 1267: 1256: 1255: 1230: 1229: 1216: 1203: 1202: 1191: 1190: 1151: 1138: 1136: 1135: 1130: 1113: 1112: 1101: 1100: 1090: 1089: 1071: 1070: 1059: 1058: 1036: 1035: 1028: 1010: 1009: 990: 988: 987: 982: 968: 967: 956: 955: 934: 932: 931: 926: 893: 891: 890: 885: 877: 876: 875: 833: 831: 830: 825: 823: 819: 779: 761: 760: 759: 723: 721: 720: 715: 701: 700: 690: 675: 674: 591: 589: 588: 583: 569: 568: 567: 555: 554: 544: 455: 453: 452: 447: 433: 432: 421: 420: 394:dependent family 350: 347: 344: 341: 338: 335: 332: 329: 326: 323: 320: 317: 314: 311: 308: 305: 302: 299: 296: 293: 290: 287: 284: 281: 278: 275: 272: 269: 266: 263: 260: 257: 254: 251: 248: 219: 216: 213: 210: 207: 204: 201: 198: 195: 192: 189: 186: 183: 180: 177: 174: 162:Peano's encoding 118: 111: 107: 104: 98: 96: 62:"Inductive type" 55: 31: 23: 2413: 2412: 2408: 2407: 2406: 2404: 2403: 2402: 2388: 2387: 2369: 2354: 2351: 2350: 2312: 2311: 2307: 2267: 2266: 2262: 2246: 2245: 2241: 2226: 2193: 2192: 2188: 2172: 2171: 2167: 2145: 2144: 2140: 2125: 2092: 2091: 2087: 2072: 2061: 2054: 2053: 2049: 2044: 2031: 2022: 2004: 1988: 1981: 1971: 1926: 1925: 1921: 1915: 1897: 1892: 1891: 1888: 1885: 1882: 1879: 1876: 1873: 1870: 1867: 1864: 1861: 1858: 1855: 1852: 1849: 1846: 1843: 1840: 1837: 1834: 1831: 1828: 1825: 1822: 1819: 1816: 1813: 1810: 1807: 1804: 1801: 1798: 1795: 1792: 1789: 1786: 1783: 1780: 1777: 1774: 1771: 1768: 1765: 1762: 1759: 1756: 1753: 1750: 1747: 1744: 1741: 1738: 1735: 1732: 1722:natural numbers 1710: 1611: 1453: 1386: 1379: 1372: 1371: 1320: 1309: 1308: 1249: 1217: 1184: 1152: 1145: 1144: 1094: 1052: 993: 992: 949: 944: 943: 938: 896: 895: 866: 846: 845: 844:. The value of 839: 821: 820: 808: 781: 780: 768: 750: 726: 725: 668: 645: 644: 642: 638: 627: 621: 613: 607: 603: 595: 548: 535: 534: 528: 522: 512: 487: 483: 479: 475: 471: 463: 459: 414: 409: 408: 406: 402: 398: 391: 387: 384:. Given a type 379: 366: 361: 359:Implementations 352: 351: 348: 345: 342: 339: 336: 333: 330: 327: 324: 321: 318: 315: 312: 309: 306: 303: 300: 297: 294: 291: 288: 285: 282: 279: 276: 273: 270: 267: 264: 261: 258: 255: 252: 249: 246: 240: 221: 220: 217: 214: 211: 208: 205: 202: 199: 196: 193: 190: 187: 184: 181: 178: 175: 172: 158:natural numbers 135:data structures 131:inductive types 129:, a system has 119: 108: 102: 99: 56: 54: 44: 32: 21: 12: 11: 5: 2411: 2409: 2401: 2400: 2390: 2389: 2386: 2385: 2380: 2375: 2368: 2367:External links 2365: 2364: 2363: 2349: 2348: 2305: 2260: 2239: 2224: 2186: 2165: 2138: 2123: 2085: 2070: 2046: 2045: 2043: 2040: 2039: 2038: 2030: 2027: 2019: 2018: 1998: 1997: 1970: 1967: 1954: 1951: 1948: 1945: 1942: 1939: 1936: 1933: 1914: 1911: 1907:Universe types 1896: 1893: 1731: 1720:predicates on 1709: 1706: 1657: 1654: 1651: 1648: 1645: 1642: 1639: 1636: 1633: 1630: 1625: 1622: 1619: 1616: 1609: 1606: 1603: 1600: 1597: 1594: 1589: 1586: 1583: 1578: 1575: 1572: 1569: 1566: 1563: 1560: 1557: 1554: 1551: 1548: 1544: 1540: 1537: 1534: 1531: 1528: 1525: 1522: 1517: 1514: 1511: 1508: 1505: 1502: 1498: 1494: 1491: 1487: 1484: 1481: 1478: 1475: 1470: 1467: 1464: 1458: 1452: 1449: 1446: 1443: 1440: 1437: 1434: 1430: 1427: 1424: 1421: 1417: 1414: 1411: 1408: 1403: 1400: 1397: 1391: 1385: 1382: 1357: 1354: 1351: 1348: 1345: 1342: 1337: 1334: 1331: 1325: 1319: 1316: 1286: 1280: 1277: 1274: 1271: 1266: 1263: 1260: 1254: 1248: 1245: 1242: 1239: 1236: 1233: 1228: 1225: 1222: 1215: 1212: 1209: 1206: 1201: 1198: 1195: 1189: 1183: 1180: 1177: 1174: 1171: 1168: 1165: 1161: 1158: 1155: 1128: 1125: 1122: 1119: 1116: 1111: 1108: 1105: 1099: 1093: 1088: 1083: 1080: 1077: 1074: 1069: 1066: 1063: 1057: 1051: 1048: 1045: 1042: 1039: 1034: 1027: 1024: 1021: 1017: 1013: 1008: 1005: 1002: 980: 977: 974: 971: 966: 963: 960: 954: 936: 924: 921: 918: 915: 912: 909: 906: 903: 883: 880: 874: 869: 865: 862: 859: 856: 853: 835: 818: 814: 811: 809: 807: 804: 801: 798: 795: 792: 789: 786: 783: 782: 778: 774: 771: 769: 767: 764: 758: 753: 749: 746: 743: 740: 737: 734: 733: 713: 710: 707: 704: 699: 696: 693: 689: 685: 682: 679: 673: 667: 664: 661: 658: 655: 652: 640: 636: 623: 619: 609: 605: 604:is defined by 601: 593: 581: 578: 575: 572: 566: 562: 559: 553: 547: 543: 524: 518: 508: 485: 481: 477: 473: 469: 461: 457: 445: 442: 439: 436: 431: 428: 425: 419: 404: 400: 396: 389: 385: 377: 365: 364:W- and M-types 362: 360: 357: 245: 239: 236: 171: 121: 120: 35: 33: 26: 13: 10: 9: 6: 4: 3: 2: 2410: 2399: 2396: 2395: 2393: 2384: 2381: 2379: 2376: 2374: 2371: 2370: 2366: 2360: 2359: 2353: 2352: 2343: 2338: 2333: 2332:10.1.1.166.34 2328: 2324: 2320: 2316: 2309: 2306: 2301: 2297: 2293: 2289: 2284: 2279: 2275: 2271: 2264: 2261: 2255: 2250: 2243: 2240: 2235: 2231: 2227: 2225:9783939897873 2221: 2216: 2211: 2206: 2201: 2197: 2190: 2187: 2181: 2176: 2169: 2166: 2161: 2157: 2153: 2149: 2142: 2139: 2134: 2130: 2126: 2124:9783939897873 2120: 2115: 2110: 2105: 2100: 2096: 2089: 2086: 2081: 2077: 2073: 2067: 2060: 2059: 2051: 2048: 2041: 2036: 2033: 2032: 2028: 2026: 2015: 2011: 2007: 2003: 2002: 2001: 1995: 1991: 1987: 1986: 1985: 1978: 1976: 1968: 1966: 1952: 1949: 1946: 1943: 1937: 1934: 1931: 1919: 1912: 1910: 1908: 1904: 1901: 1894: 1729: 1727: 1723: 1719: 1715: 1707: 1705: 1703: 1699: 1695: 1690: 1688: 1684: 1680: 1676: 1671: 1652: 1646: 1643: 1637: 1634: 1631: 1601: 1598: 1595: 1573: 1570: 1564: 1561: 1558: 1555: 1552: 1546: 1542: 1532: 1526: 1520: 1512: 1506: 1503: 1500: 1496: 1492: 1489: 1485: 1479: 1473: 1468: 1465: 1462: 1444: 1438: 1435: 1432: 1428: 1425: 1422: 1419: 1412: 1406: 1401: 1398: 1395: 1383: 1380: 1369: 1355: 1346: 1340: 1335: 1332: 1329: 1317: 1314: 1306: 1302: 1297: 1284: 1275: 1269: 1264: 1261: 1258: 1246: 1240: 1237: 1234: 1210: 1204: 1199: 1196: 1193: 1175: 1169: 1166: 1163: 1159: 1156: 1153: 1142: 1126: 1120: 1114: 1109: 1106: 1103: 1078: 1072: 1067: 1064: 1061: 1043: 1037: 1025: 1022: 1019: 1015: 1011: 975: 969: 964: 961: 958: 940: 916: 910: 907: 901: 867: 860: 857: 851: 843: 838: 812: 810: 799: 793: 790: 784: 772: 770: 751: 744: 741: 735: 708: 702: 694: 691: 683: 680: 665: 659: 653: 650: 633: 631: 626: 617: 612: 599: 576: 570: 560: 557: 545: 532: 527: 521: 516: 511: 506: 502: 498: 493: 491: 467: 440: 434: 429: 426: 423: 395: 383: 375: 371: 363: 358: 356: 243: 237: 235: 233: 228: 226: 169: 167: 163: 159: 154: 152: 148: 144: 140: 136: 132: 128: 117: 114: 106: 95: 92: 88: 85: 81: 78: 74: 71: 67: 64: –  63: 59: 58:Find sources: 52: 48: 42: 41: 36:This article 34: 30: 25: 24: 19: 2357: 2322: 2318: 2308: 2283:math/0409158 2276:(1): 40–59. 2273: 2269: 2263: 2242: 2195: 2189: 2168: 2151: 2147: 2141: 2094: 2088: 2057: 2050: 2020: 2013: 2009: 2005: 2000:and a loop; 1999: 1993: 1989: 1979: 1972: 1916: 1905: 1898: 1757:zero_is_even 1713: 1711: 1692:M-types are 1691: 1672: 1370: 1298: 941: 841: 836: 634: 629: 624: 615: 610: 597: 530: 525: 519: 514: 509: 504: 500: 496: 494: 370:well-founded 368:W-types are 367: 353: 241: 229: 222: 168:as follows: 155: 130: 124: 109: 103:January 2018 100: 90: 83: 76: 69: 57: 45:Please help 40:verification 37: 2398:Type theory 2325:(1): 3–27. 2035:Coinduction 1698:coinductive 1675:isomorphism 456:. The type 238:Elimination 232:predicative 127:type theory 2254:1504.05531 2205:1504.02949 2104:1504.02949 2071:8870881059 2042:References 73:newspapers 2327:CiteSeerX 2180:1201.3898 1941:→ 1733:Inductive 1543:⊢ 1497:∏ 1451:→ 1353:→ 1182:→ 1092:→ 1050:→ 1016:∏ 991:has type 911:⁡ 861:⁡ 794:⁡ 745:⁡ 654:⁡ 372:types in 173:Inductive 143:relations 2392:Category 2234:15020752 2133:15020752 2080:12731401 2029:See also 2008: : 1992: : 639: : 596: : 513: : 472: : 399: : 388: : 247:nat_elim 1702:streams 1143:proof, 139:numbers 87:scholar 2329:  2300:360990 2298:  2232:  2222:  2131:  2121:  2078:  2068:  2023:circle 1994:circle 1982:circle 1853:forall 1781:forall 1718:parity 724:where 392:and a 334:forall 295:forall 256:forall 160:using 145:, and 89:  82:  75:  68:  60:  2296:S2CID 2278:arXiv 2249:arXiv 2230:S2CID 2200:arXiv 2175:arXiv 2129:S2CID 2099:arXiv 2062:(PDF) 1874:-> 1832:-> 1802:-> 1745:-> 834:and 1 592:with 466:arity 380:be a 328:-> 310:-> 289:-> 268:-> 212:-> 147:trees 94:JSTOR 80:books 2220:ISBN 2119:ISBN 2076:OCLC 2066:ISBN 2014:base 2010:base 2006:loop 1990:base 1868:even 1835:Prop 1820:with 1805:even 1763:even 1748:Prop 1736:even 1714:some 1694:dual 651:List 628:) = 614:) = 495:Let 480:has 271:Prop 182:Type 66:news 2337:doi 2323:342 2288:doi 2274:146 2210:doi 2156:doi 2152:176 2109:doi 1889:)). 1877:odd 1862:nat 1829:nat 1823:odd 1796:odd 1790:nat 1742:nat 1726:Coq 1677:as 908:inr 858:inl 791:inr 742:inl 643:as 523:, 2 517:, 1 349:)). 265:nat 215:nat 209:nat 197:nat 176:nat 166:Coq 125:In 49:by 2394:: 2335:. 2321:. 2317:. 2294:. 2286:. 2272:. 2228:. 2218:. 2208:. 2150:. 2127:. 2117:. 2107:. 2074:. 2012:= 1965:. 1838::= 1817:)) 1751::= 1728:: 666::= 622:(2 608:(1 600:→ 546::= 503:, 499:, 492:. 403:→ 325:)) 185::= 153:. 141:, 2345:. 2339:: 2302:. 2290:: 2280:: 2257:. 2251:: 2236:. 2212:: 2202:: 2183:. 2177:: 2162:. 2158:: 2135:. 2111:: 2101:: 2082:. 2016:. 1953:e 1950:p 1947:y 1944:T 1938:A 1935:: 1932:B 1922:A 1886:n 1883:S 1880:( 1871:n 1865:, 1859:: 1856:n 1850:( 1847:: 1841:| 1826:: 1814:n 1811:S 1808:( 1799:n 1793:, 1787:: 1784:n 1778:( 1775:: 1769:| 1766:O 1760:: 1754:| 1739:: 1656:) 1653:w 1650:( 1647:C 1644:: 1641:) 1638:h 1635:, 1632:w 1629:( 1624:m 1621:i 1618:l 1615:e 1608:) 1605:) 1602:f 1599:, 1596:a 1593:( 1588:p 1585:u 1582:s 1577:( 1574:C 1571:: 1568:) 1565:c 1562:, 1559:f 1556:, 1553:a 1550:( 1547:h 1539:) 1536:) 1533:b 1530:( 1527:f 1524:( 1521:C 1516:) 1513:a 1510:( 1507:B 1504:: 1501:b 1493:: 1490:c 1486:, 1483:) 1480:x 1477:( 1474:B 1469:A 1466:: 1463:x 1457:W 1448:) 1445:a 1442:( 1439:B 1436:: 1433:f 1429:, 1426:A 1423:: 1420:a 1416:) 1413:a 1410:( 1407:B 1402:A 1399:: 1396:a 1390:W 1384:: 1381:w 1356:U 1350:) 1347:x 1344:( 1341:B 1336:A 1333:: 1330:x 1324:W 1318:: 1315:C 1285:. 1279:) 1276:x 1273:( 1270:B 1265:A 1262:: 1259:x 1253:W 1247:: 1244:) 1241:f 1238:, 1235:a 1232:( 1227:p 1224:u 1221:s 1214:) 1211:x 1208:( 1205:B 1200:A 1197:: 1194:x 1188:W 1179:) 1176:a 1173:( 1170:B 1167:: 1164:f 1160:A 1157:: 1154:a 1127:. 1124:) 1121:x 1118:( 1115:B 1110:A 1107:: 1104:x 1098:W 1087:) 1082:) 1079:x 1076:( 1073:B 1068:A 1065:: 1062:x 1056:W 1047:) 1044:a 1041:( 1038:B 1033:( 1026:A 1023:: 1020:a 1012:: 1007:p 1004:u 1001:s 979:) 976:x 973:( 970:B 965:A 962:: 959:x 953:W 937:a 923:) 920:) 917:a 914:( 905:( 902:f 882:) 879:) 873:1 868:1 864:( 855:( 852:f 842:1 837:1 817:1 813:= 806:) 803:) 800:a 797:( 788:( 785:f 777:0 773:= 766:) 763:) 757:1 752:1 748:( 739:( 736:f 712:) 709:x 706:( 703:f 698:) 695:A 692:+ 688:1 684:: 681:x 678:( 672:W 663:) 660:A 657:( 641:U 637:A 630:1 625:2 620:f 616:0 611:2 606:f 602:U 598:2 594:f 580:) 577:x 574:( 571:f 565:2 561:: 558:x 552:W 542:N 531:2 529:: 526:2 520:2 515:1 510:1 505:2 501:1 497:0 486:a 484:( 482:B 478:a 474:A 470:a 462:B 458:A 444:) 441:a 438:( 435:B 430:A 427:: 424:a 418:W 405:U 401:A 397:B 390:U 386:A 378:U 346:n 343:P 340:, 337:n 331:( 322:n 319:S 316:( 313:P 307:n 304:P 301:, 298:n 292:( 286:) 283:0 280:P 277:( 274:, 262:: 259:P 253:( 250:: 218:. 206:: 203:S 200:| 194:: 191:0 188:| 179:: 116:) 110:( 105:) 101:( 91:· 84:· 77:· 70:· 43:. 20:.

Index

Inductive data type

verification
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"Inductive type"
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type theory
data structures
numbers
relations
trees
structural recursion
natural numbers
Peano's encoding
Coq
successor function
predicative
well-founded
intuitionistic type theory
universe of types
dependent family
arity
polynomial functor
natural deduction

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