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Show HN: Program will only compile if the grid on line 30 is a magic square

10 points by amenghra 3y ago

amenghra 3y ago
It's ugly and hardcoded for a 3x3 grid. Can we improve this? Slightly better: https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQA4CcD2BzJBDAtqA7tADaGgoB2hAnqAMYrYJECmo0AZqAC6QsbQAmpMqELQyLAMwAGVvEyhsmNNBqhYARwCumJCwLc1m7PACMAVgB0AWABQnSghYBBBI7L8APOFBMAHpyZ3OTJKAG0AXQAaUABVAD5QAF5QUIs08GiY8IBuW1t7R1AAYV1MAKckJAB5NgAZQI9bUGbQADlIppaizUqKpB9-QP5gsPCklPDOhOTu3srQgCJCQLRuBbG-AKC2zuaAfmKepD7d0AAuYtLyypr6sg920Bc3T1njyujMELi43Jt8hwsABi7ACgXGJSYZSYfVuDXMcQBhXAHic0QAQtEitMUmkLJDobC6g0nHFoniCddqsT7uiyaAKVcYTcaR5sRtBtsQWwwcIDpwkJoWBc2JhCLAmEjnO5UQMtsNQAAjFAoZZfaIADRxTjlQ3gAqFoAOGvOoFF4sldkBoAA4kgBKiMViOjYWm6WgARaIAUWiQJd7vdNuiAAlogBJaanQNOGUotGgTHFemxzwor2gX2gIEpuMeYOgMOgSMBwPu1NeR2gDM23NpjxJrMhuuVop+iNk6Nlt0V+M+jvRXts-u2zuu7sTpzED3sNgeUIJpNt6sj-220MR8IJH6gH7bn55K2FENQtO67ZfUY47ybPUpMRsJj9It4h9P0AAfTGBxDpsv2WaKUIEwIgvHPBVLwia9wPgUI336D9yTSeDQAAJSYWBOG-NCMM4P8QgiADQCAqdCBnNg5x1W8LwIrdxicRZljIVZIHWGDQBkflBWFToK1I8i2AAJg8E9ME8UlonAEDCFRH5B2nWcvGk2SDyPZwFIo4SqM5CCQgxdjILo5J0UYlY1g5eV4E4rhuPOXj2NEzw6SNM0xQlU1+NnLTJOUulEX+Gw6DITDSAAawuA0WGSSLQEweA7QdJoABZogATmiQSAwkaIzGiAB2AMAA5ohMaIADZ-NsEBLiYfhoE4fUUFASBOE4BBYDOEBYBQHk8B0JhsCIQgLDobBgH4JgADcmEIFBGGYgBaAomAW5ZpsIBaxTQFB7W4YwFrEJbAVgGh7QQTgwC+fgqrAFq2o6kAJvWuan1gCxsCYPA3tG4BRsYZYlugD6FrYTQyBoThoHIMUFuQdAsGwQbFsO5aTrOi6gA https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQA4CcD...
- amenghra 3y ago
  Tada: https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQA4CcD2BzJBDAtqA7tADaGgoB2hAnqAMYrYJECmo0AZqAC6QsbQAmpMqELQyLACwAmVvEyhsmNNBqhYARwCumJEwB0AWABQxkKADCuzJxaZhOrNRQdCTMmm6gAcsc6UELACCSEgAPF6gTAAeNmT88GSa2ABGTEgANKAASpExbvGgdpQA2gC6oAC8oGUAfJXZxQBEru7cjeXRsQURAPzZxqCDoABcoMFhXpnFejNZmUWlNQDcvv5BcaGBuV3wySgornaZABp1VVud+fCcSJosfccjoGyYhLBMpmDjmNSKZNAITSEazQcirAKgAASTEw-FC4G2V0KZBKi3qCMucXgxTEbDSUMyMz0uPxAH1yn1IU8iktBuCWOBMER4YiscjUWcIKyCjiyHikKBSYSZiSBVkmLBOBTshLONSUWVaaB6aAADKYSUszEFIq1dHc7FE0WCzLG1XS1XyygrIx+CEAIU0nHVmoxeTZurRVTdO2qRr5+MhpoDAvJoEpVptZnMPBoAGsuJBrIViImWExXNg3Jw5LpQPx2PzsyqAGLAzixLXunUK0qZHLauS1+p671NFoeSDtA2gAAM4eyIwGoDL1krjOZ4BqUyJc1AROhsPhNUWKsCxAAIoXNj3PZzAu23J3u42+wObnch0ZBoENuvCFu2GwpKFF3DAtOIEzCJsap-74+bDwt+v5-mum6Fi+FzVk2lCZPau61py9qHq0XYdDBZ59BeLDDMO0G+m+oT2nUfQvG8uFjBBT5QZkE4-iRNSfGMIQ-KQHAOGxfwAkCIJgraaxQjC8RVr6nr1ohqItl6ECoceGG+v2fQ5Hh15CbCsDAZOn7TLMmREURU4rkxAkQuK-CaDQTCiUi4mDqenrSZy4ByW0ClIkpg6qYM5mWdZ9HLjOelfsyhl-qupksFuSg2R6tYSQ5zZVK2snNEebk9p5KnDtFaChL5VlaT+RlBXoc4GcJy7GSqBVMC+Pq2fF9mYY5yUyS5aVoSemFZVePlMBZVn1SBU6lXOjrOhqnCvpVRkRXaUXQEo9WSWUCUtUl1Tta56GZQO2VqblL61cN2k6bOmQutNYXVZFEBYGQsAICg7yxTWqLrWJm0pWFO3dYp+19fddhPS91m1YFfrBW+mlThFZgAMpJAAtLo5YDSI6AqCqSPYG9CRJKkSBrc1X1SW1zl-e5bK9d5oC40VkO6WVwp6OMM1LnNJkLfTOBMLjsOrXW9OU518l7dhty4fhGwMzdPYI+eUtPOR7yZAjfMC4zo0iyZKoALJKCoCNaDo-lC-usua0kmnMwFOtEuAD2g69Ou5ZDR3LsLcuzX+074dRQGjhWbhVXrRh0I9crcLoTCksklCkjHTBMKMOH1OnGqgIbyg0Cb2i6KExTDsUUiZAA7JkABsdYlwAnJkACsmQAIy12pxQSJkADMmQABztxFpgAFTGAA6igSBxvAbCT6AjQ6Mk0A3DolCNGo0AAF4Spk+hoIYJgR+QkrPCgmhIPHiez+fafK1UmfwDnxum4Xxcdy3rfN6ALdd6AEjt4MYoLdeytw-qAPuTcAHVErqAKumQG7fykFAoBcDQBl1AL3b+3dB4mWHsAYwzFLADWXtcFAoBIAVgQLAYYIBYDOE4HgM22AiCED0HQbAwB+BMAAG4ZhQIwdwyMFrI1cLwwgyNXhoEnsvSA2BYDIzEEItYsAaBIABJwMAdh+DMQoZwKhNDOE8L4QEJAsA9BZjwGY9hwB2GMFcEI6AWZkZsE0GQGgnBQRkFeMjZA6AsDYGYYIxRC0VFqIQBo4wQA https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQA4CcD...
schoen 3y ago
Wow! This may help with the intuition that typechecking for some type systems is an undecidable problem.
- amenghra 3y ago
  https://beza1e1.tuxen.de/articles/accidentally_turing_complete.html https://beza1e1.tuxen.de/articles/accidentally_turing_comple... lists a few type-related things. Type inference has been proven to be undecidable in some cases (e.g. with dependent types).
  - schoen 3y ago
    Sorry, by "the intuition that..." I didn't mean "reason to believe (a result that isn't established)" but more like "an aid to understanding (a result that was already proven)". Thanks for the link!

10 points by amenghra 3y ago

It's ugly and hardcoded for a 3x3 grid. Can we improve this? Slightly better: https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQA4CcD2BzJBDAtqA7tADaGgoB2hAnqAMYrYJECmo0AZqAC6QsbQAmpMqELQyLAMwAGVvEyhsmNNBqhYARwCumJCwLc1m7PACMAVgB0AWABQnSghYBBBI7L8APOFBMAHpyZ3OTJKAG0AXQAaUABVAD5QAF5QUIs08GiY8IBuW1t7R1AAYV1MAKckJAB5NgAZQI9bUGbQADlIppaizUqKpB9-QP5gsPCklPDOhOTu3srQgCJCQLRuBbG-AKC2zuaAfmKepD7d0AAuYtLyypr6sg920Bc3T1njyujMELi43Jt8hwsABi7ACgXGJSYZSYfVuDXMcQBhXAHic0QAQtEitMUmkLJDobC6g0nHFoniCddqsT7uiyaAKVcYTcaR5sRtBtsQWwwcIDpwkJoWBc2JhCLAmEjnO5UQMtsNQAAjFAoZZfaIADRxTjlQ3gAqFoAOGvOoFF4sldkBoAA4kgBKiMViOjYWm6WgARaIAUWiQJd7vdNuiAAlogBJaanQNOGUotGgTHFemxzwor2gX2gIEpuMeYOgMOgSMBwPu1NeR2gDM23NpjxJrMhuuVop+iNk6Nlt0V+M+jvRXts-u2zuu7sTpzED3sNgeUIJpNt6sj-220MR8IJH6gH7bn55K2FENQtO67ZfUY47ybPUpMRsJj9It4h9P0AAfTGBxDpsv2WaKUIEwIgvHPBVLwia9wPgUI336D9yTSeDQAAJSYWBOG-NCMM4P8QgiADQCAqdCBnNg5x1W8LwIrdxicRZljIVZIHWGDQBkflBWFToK1I8i2AAJg8E9ME8UlonAEDCFRH5B2nWcvGk2SDyPZwFIo4SqM5CCQgxdjILo5J0UYlY1g5eV4E4rhuPOXj2NEzw6SNM0xQlU1+NnLTJOUulEX+Gw6DITDSAAawuA0WGSSLQEweA7QdJoABZogATmiQSAwkaIzGiAB2AMAA5ohMaIADZ-NsEBLiYfhoE4fUUFASBOE4BBYDOEBYBQHk8B0JhsCIQgLDobBgH4JgADcmEIFBGGYgBaAomAW5ZpsIBaxTQFB7W4YwFrEJbAVgGh7QQTgwC+fgqrAFq2o6kAJvWuan1gCxsCYPA3tG4BRsYZYlugD6FrYTQyBoThoHIMUFuQdAsGwQbFsO5aTrOi6gA https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQA4CcD...

amenghra 3y ago
Tada: https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQA4CcD2BzJBDAtqA7tADaGgoB2hAnqAMYrYJECmo0AZqAC6QsbQAmpMqELQyLACwAmVvEyhsmNNBqhYARwCumJEwB0AWABQxkKADCuzJxaZhOrNRQdCTMmm6gAcsc6UELACCSEgAPF6gTAAeNmT88GSa2ABGTEgANKAASpExbvGgdpQA2gC6oAC8oGUAfJXZxQBEru7cjeXRsQURAPzZxqCDoABcoMFhXpnFejNZmUWlNQDcvv5BcaGBuV3wySgornaZABp1VVud+fCcSJosfccjoGyYhLBMpmDjmNSKZNAITSEazQcirAKgAASTEw-FC4G2V0KZBKi3qCMucXgxTEbDSUMyMz0uPxAH1yn1IU8iktBuCWOBMER4YiscjUWcIKyCjiyHikKBSYSZiSBVkmLBOBTshLONSUWVaaB6aAADKYSUszEFIq1dHc7FE0WCzLG1XS1XyygrIx+CEAIU0nHVmoxeTZurRVTdO2qRr5+MhpoDAvJoEpVptZnMPBoAGsuJBrIViImWExXNg3Jw5LpQPx2PzsyqAGLAzixLXunUK0qZHLauS1+p671NFoeSDtA2gAAM4eyIwGoDL1krjOZ4BqUyJc1AROhsPhNUWKsCxAAIoXNj3PZzAu23J3u42+wObnch0ZBoENuvCFu2GwpKFF3DAtOIEzCJsap-74+bDwt+v5-mum6Fi+FzVk2lCZPau61py9qHq0XYdDBZ59BeLDDMO0G+m+oT2nUfQvG8uFjBBT5QZkE4-iRNSfGMIQ-KQHAOGxfwAkCIJgraaxQjC8RVr6nr1ohqItl6ECoceGG+v2fQ5Hh15CbCsDAZOn7TLMmREURU4rkxAkQuK-CaDQTCiUi4mDqenrSZy4ByW0ClIkpg6qYM5mWdZ9HLjOelfsyhl-qupksFuSg2R6tYSQ5zZVK2snNEebk9p5KnDtFaChL5VlaT+RlBXoc4GcJy7GSqBVMC+Pq2fF9mYY5yUyS5aVoSemFZVePlMBZVn1SBU6lXOjrOhqnCvpVRkRXaUXQEo9WSWUCUtUl1Tta56GZQO2VqblL61cN2k6bOmQutNYXVZFEBYGQsAICg7yxTWqLrWJm0pWFO3dYp+19fddhPS91m1YFfrBW+mlThFZgAMpJAAtLo5YDSI6AqCqSPYG9CRJKkSBrc1X1SW1zl-e5bK9d5oC40VkO6WVwp6OMM1LnNJkLfTOBMLjsOrXW9OU518l7dhty4fhGwMzdPYI+eUtPOR7yZAjfMC4zo0iyZKoALJKCoCNaDo-lC-usua0kmnMwFOtEuAD2g69Ou5ZDR3LsLcuzX+074dRQGjhWbhVXrRh0I9crcLoTCksklCkjHTBMKMOH1OnGqgIbyg0Cb2i6KExTDsUUiZAA7JkABsdYlwAnJkACsmQAIy12pxQSJkADMmQABztxFpgAFTGAA6igSBxvAbCT6AjQ6Mk0A3DolCNGo0AAF4Spk+hoIYJgR+QkrPCgmhIPHiez+fafK1UmfwDnxum4Xxcdy3rfN6ALdd6AEjt4MYoLdeytw-qAPuTcAHVErqAKumQG7fykFAoBcDQBl1AL3b+3dB4mWHsAYwzFLADWXtcFAoBIAVgQLAYYIBYDOE4HgM22AiCED0HQbAwB+BMAAG4ZhQIwdwyMFrI1cLwwgyNXhoEnsvSA2BYDIzEEItYsAaBIABJwMAdh+DMQoZwKhNDOE8L4QEJAsA9BZjwGY9hwB2GMFcEI6AWZkZsE0GQGgnBQRkFeMjZA6AsDYGYYIxRC0VFqIQBo4wQA https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQA4CcD...

schoen 3y ago

Wow! This may help with the intuition that typechecking for some type systems is an undecidable problem.

amenghra 3y ago
https://beza1e1.tuxen.de/articles/accidentally_turing_complete.html https://beza1e1.tuxen.de/articles/accidentally_turing_comple... lists a few type-related things. Type inference has been proven to be undecidable in some cases (e.g. with dependent types).
- schoen 3y ago
  Sorry, by "the intuition that..." I didn't mean "reason to believe (a result that isn't established)" but more like "an aid to understanding (a result that was already proven)". Thanks for the link!