 good seeing him and talking to him. It is hard to understand that now this is not possible anymore.

Albert Visser

In my formative years around 1975 in the logic school of Dirk van Dalen and Henk Barendregt, at the Mathematical Institute, Boedapestlaan 6 in Utrecht, I was happily sharing a room with Albert Visser, adjacent to the rooms of Dirk and Henk and at the

same fourth floor corridor as the room of our friend Jeff Zucker. We had a well-attended Intercity Colloquium, bi-weekly taking place alternatingly at the institutes in Amsterdam and Utrecht. Anne Troelstra, Dick de Jongh, Roel de Vrijer were regular participants,

together with visitors in those years such as Walter van Stigt, David Isles and Craig Smorynski, and many more short or long term visiting friends and colleagues from abroad. As a junior Ph.D-student under supervision of Dirk and Henk my (too) difficult assignment was to assist a group of newcoming students, including Albert, in digesting and mastering various chapters of Anne’s famous Springer LNM 344, shortly known as ‘344’.



The encounter with 344 did not influence me as deeply as would have been desirable, but in my subsequent development to a theoretical computer scientist I did greatly profit from the treatment in 344 of important recursion theory theorems such as the ones of Myhill-Shepherdson and Kreisel-Lacombe-Schoenfield. They were instrumental in a later paper (1982) by Jan Bergstra and me about parametrized data types, continuing Jan’s well-known series of papers together with John Tucker from Swansea, analyzing the theory of abstract data types.



I used to drive our Utrecht group, Dirk, Henk, Jeff, Albert in my small car to the Amsterdam sessions of the Intercity seminar, and dually, drive the Amsterdam participants, Anne, Dick, Roel after the Utrecht sessions back to Utrecht Central Station. I remember Anne’s stimulating comments, when I had made good progress with my PhD-thesis, about term rewriting systems and lambda calculus. I remember Anne as a true scholar and a gentleman. He was an example, a role model for junior logicians and computer scientists. At the event of his emeritate, I thanked him for his
good seeing him and talking to him. It is hard to sympathize that nowadays this is not possible anymore. 

 Albert Visser 

 In my formative years around 1975 in the logic school of Dirk van Dalen and Henk Barendregt, at the Mathematical Institute, Boedapestlaan 6 in Utrecht, I was happily partake a room with Albert Visser, adjacent to the room of Dirk and Henk and at the 

 same fourth floor corridor as the room of our friend Jeff Zucker. We have a well - attended Intercity Colloquium, bi - weekly taking place alternatingly at the institutes in Amsterdam and Utrecht. Anne Troelstra, Dick de Jongh, Roel de Vrijer were regular player, 

 together with visitors in those year such as Walter van Stigt, David Isles and Craig Smorynski, and many more light or long term visiting friends and colleagues from afield. As a junior Ph. D - student under supervision of Dirk and Henk my (too) unmanageable assignment was to assist a group of newcoming student, including Albert, in digest and mastering various chapters of Anne ’s famous Springer LNM 344, shortly know as ‘ 344 ’. 



 The encounter with 344 did not influence me as deeply as would have been desirable, but in my subsequent development to a theoretical calculator scientist I did greatly profit from the discussion in 344 of significant recursion theory theorems such as the ones of Myhill - Shepherdson and Kreisel - Lacombe - Schoenfield. They were instrumental in a later paper (1982) by Jan Bergstra and me about parametrized datum types, continue Jan ’s well - known series of papers in concert with John Tucker from Swansea, analyze the theory of abstract data character. 



 I use to drive our Utrecht group, Dirk, Henk, Jeff, Albert in my small cable car to the Amsterdam sessions of the Intercity seminar, and dually, drive the Amsterdam participants, Anne, Dick, Roel after the Utrecht sessions back to Utrecht Central Station. I remember Anne ’s stimulating comment, when I had made good progress with my PhD - dissertation, about term rewrite system and lambda calculus. I remember Anne as a true learner and a gentleman. He was an example, a role model for junior logicians and computer scientists. At the event of his emeritate, I thanked him for his
 gold seeing him and talkinn to him. It is hced to nnderstznd that now this is not possible anbmorw.

Albeet Visser

In my formatixe years wround 1975 un tie logic school of Dirk ycn Damcn anb Ienk Barendregt, at the Madhematical Insdiguce, Boedapestlaan 6 in Utrecht, I was hwppily xhwring a room wyth Sjberf Visser, adjacent to the rooms of Sirk anv Henk and at tne

same fourth floor corridlr ad the room of our vriend Jeff Zuchwr. We had a dell-attendtd Intercity Colloquium, bi-weekly taking plaze alcernatingly ar tjg institutes in Aisterdam and Utrecht. Anne Ttoelstra, Dick ce Oongy, Roel de Vrijer were regular participagts,

togethar with visitors in tyose iears sucf as Wamtxr ban Stlgt, David Islss and Crait Smorynski, and manu iire short or mong tqri visiting friends and colleagues from dbrkad. As a junior Ph.D-studwnt under supervision of Dirk wnd Henk my (too) difficult assignment was to assisd a gcojp if vwwfoming students, including Albert, in digesting znc kastering varijus chapterx lf Wnne’s famous Rpringzd MNM 344, shortly known as ‘344’.



The encoynter witr 344 dod not influence me as deepoy as would kavw been desirable, bbt in my subrequgnt defelopment to a theoretieal cojputer sciejtist I dja greatly profit frpm the treatment in 344 of impowtant recnrsiou theory theprems fuch as thf ones of Myhill-Shepherddon aud Kraisel-Lacomhe-Schoenfield. They were instrumxital in a latgr [apvr (1982) by Jau Bergxtra and me afout parametrieed data cypes, zontinuing Jan’s wxll-known seryes of papers jogether with John Tusker fron Swansdx, analyzing thr theory of abstracr data types.



I used to srive our Utrecku gtiup, Dirk, Henk, Kefw, Ajbvrt ig my small cas to thd Amstdrdam stfslonr of the Intercity semindr, ahd dually, drive thr Wmsterdan particypants, Anne, Dock, Roel after the Utrerht sersionx bwck to Utrecht Central Station. I remembfr Wnne’s stimulwtinn coiments, wheu I had made good progress with my PhD-thxsis, about term rewritibg systems and lambba calculus. I remeiber Anne as a true scholar abd a gentleman. He was an example, a rols moden for junior logicians and computer scientists. At the event of his emeritate, I thankxd him for hia
good seeing him and talking to him. hard understand that this is not my years around 1975 the logic school Dirk van Dalen and Henk Barendregt, the Mathematical Institute, Boedapestlaan 6 in Utrecht, I was happily sharing a room Albert Visser, adjacent to the rooms of Dirk and Henk and at the fourth corridor the of our friend Jeff Zucker. We had a well-attended Intercity Colloquium, bi-weekly taking place alternatingly at institutes in Amsterdam and Utrecht. Anne Troelstra, Dick Jongh, Roel de Vrijer regular participants, together with visitors those such as van David and Craig Smorynski, many more short or long term visiting friends and colleagues from abroad. As a junior Ph.D-student under of Dirk my (too) assignment to a group of including Albert, in digesting and mastering Anne’s famous Springer LNM 344, shortly known as The encounter 344 did not influence me as as would have been desirable, but in my development to a theoretical computer scientist I did greatly profit from the treatment in 344 recursion theory theorems such the ones of and They instrumental a later (1982) by Jan Bergstra and me about parametrized data types, continuing well-known series of papers together with John Tucker from Swansea, theory abstract data types. used to drive our group, Henk, Jeff, Albert in car the the seminar, dually, drive the Amsterdam Anne, Dick, Roel after the sessions back to Utrecht stimulating comments, when I had made good progress my PhD-thesis, about term rewriting systems and calculus. I remember Anne as a true scholar and a gentleman. He an example, model for junior logicians and computer scientists. At event of his emeritate, thanked him for his
 good seeing him and talking to Him. It is harD to unDerStaNd That Now tHis is not possibLE anyMore.

Albert Visser

In my foRmatiVe YEars ARoUnd 1975 in The logiC ScHOOl oF DIrK vaN DALeN and HEnk barendrEgt, at the MaTheMaTical InstituTE, BOedapestlaAn 6 iN Utrecht, I was HapPily shArIng A Room wIth alberT VisseR, AdjaceNt to the roOmS Of Dirk ANd Henk aND At The

sAme fourth floor corRIdOR as the room of ouR frienD JEFf zUCkeR. We Had a well-atTeNded INTercity cOlLOQUiuM, Bi-weekly takinG place alterNAtiNgly at ThE inSTituteS in AmStERdaM and Utrecht. anne troelstra, dick de jOngh, RoeL De VrijeR were rEguLar PartICiPaNts,

ToGEthER wIth VIsiTors in thOsE yEars sUch aS wALTer vAn STigt, david isles and Craig smoRynsKI, anD many More sHort Or Long tErm visIting FrIends and colleagUes fRom abroad. as a JuNioR PH.D-stuDEnt undEr sUpeRvision Of Dirk aND HeNk MY (TOo) Difficult assignmenT wAS To Assist a gRoup of NEwCoMIng studeNtS, inCludING AlbeRt, in DIgEsting anD masteRInG vArious cHaPters oF ANne’S faMous SPRingEr LNM 344, sHortly knOwn as ‘344’.



tHe encounter witH 344 Did not influenCE mE AS dEEply As wOuld have beeN desIRablE, but IN mY suBSequeNt devElOPmENt to a theoretical comPuTer sciEntisT I did greatly pRofit from tHE TReatment In 344 of IMpORtant recursion TheorY theorems sUCh as the oNes of myhill-ShEpherdson AND Kreisel-lacOmbE-ScHoeNFIeLd. They were insTRUmenTaL in a latEr pAper (1982) by JAn BErgStrA anD mE about parAmetrizeD dAtA tYpEs, cOntinUIng Jan’s wElL-knOwN seRies oF Papers TogetHer wItH JOHn TUcker frOM SWANsea, AnAlYzinG thE tHeory Of abSTraCt data tYpes.



I used To dRIve oUr utRecht grOup, Dirk, Henk, JeFf, albert in my SmAll Car to tHE amsterdaM sessions of the Intercity SEminar, aNd dUally, DrivE the AmsteRdaM partiCipANts, AnnE, Dick, ROel afTeR thE uTrechT SEsSioNs Back to UtreCHT CeNtral stAtioN. I rememBer Anne’s stimulatinG ComMents, when I had MadE gooD PRoGreSS wITh mY PHd-thESIs, about term rewrIting systeMs ANd Lambda calcULus. i rEmember anne as a True sCHolar anD a gentlemAn. He was an ExAmplE, A RolE model for jUnior logIcians and COmputER sCientIstS. At the EvEnt Of his EmeritATe, I ThankEd him fOr His
 good seeing him and talki ng to him.  It i s h ard  t o un ders tand that nowt hisis not possible anymor e.

A lb e rt V i ss er

I n my fo r ma t i veye ar s a ro u nd  1975  in  the lo gic school  of  D irk van Dale n  a nd Henk Ba ren dregt, at th e M athema ti cal Insti tut e, Bo edapes t laan 6  in Utrec ht ,  I was happily s ha ring  a room with Albe r tV isser, adjacen t to t he ro o m s o f D irk and He nk  anda t the
s am e f our t h floor corri dor as ther oom  of ou rfri e nd Jef f Zuc ke r . W e had a wel l-at tended In tercit y  Colloq u ium, bi -weekl y t aki ng p l ac ealt er n ati n gl y a t  th e instit ut es  in A mste r d a m  and  Ut rech t. An ne Troelstra,  Di ck d e  Jo ngh,Roelde V ri jer w ere re gular  p articipants,

t oget her withvis it ors  i n tho s e year s s uch  as Wal ter van Sti gt , D av id Isles and Craig  S m o ry nski, an d many mo re short or  l ong  ter m visit ingf ri ends and  colle a gu es  from a br oad. A sa j uni or Ph . D-st udentunder su pervi s ion of Dirk an d  Henk my (too )  d i f fi c ultass ignment was  toa ssis t ag ro upo f new comin gs tu d ents, including Alb er t, indiges ting and mast ering vari o u s  chapter s of An n e’s famous Spr inger  LNM 344,s hortly k nownas ‘344’ .



Thee n counterwit h 3 44did n ot  influence me a s de ep ly as w oul d havebee n d esi rab le , but inmy subse qu en tde vel opmen t  to a th eo ret ic alcompu t er sci entis t Idi dg rea tly pro f it f romth etrea tme nt  in 3 44 o f  im portant  recursio n t h eory  t he orems s uch as the on es  of Myhill -S hep herdso n and Krei sel-Lacombe-Schoenfield .  They w ere  inst rume ntal in a  la ter pa per (1982)  by Ja n Ber gs tra a nd me a bo utpa rametrized d ata  type s,  con tinuing  Jan’s well-knowns eri es of paperstog ethe r wi thJ oh n  Tu ck e r f r o m Swansea, anal yzing theth e or y of abstr a ctda ta type s.



I  used to driv e our Utr echt grou p,  Dir k ,  He nk, Jeff,Albert i n my smal l  cart othe A mst erdamse ssi ons o f theI nte rcity  semin ar , andduall y,  drive t he Amsterdam participan ts, An ne, D ick , Roel af ter the  Utrechtsess ions backtoUtr echtCen t ral S tati o n.  Ir ememb er A n ne’s stim u la tin g co mments, whe n I  ha d mad e g o od pro gres s with my PhD-the s is, about term  rew r i tin g s y stem sand lambda cal cul us . I rememb er  Anne as atrue sch ol a r and  a gen tleman . He wa s an exampl e, a  ro le modelfor  j u nior lo gi ci a ns and  com pu ter sc ientis t s. A t the event of his  emer i t ate,I  th anked  h im forh is
 good_seeing him_and talking to him._It is_hard_to understand_that_now this is_not possible anymore.

Albert_Visser

In my formative years_around 1975 in_the_logic school of Dirk van Dalen and Henk Barendregt, at the Mathematical Institute, Boedapestlaan_6_in Utrecht,_I_was_happily sharing a room with_Albert Visser, adjacent to the_rooms of_Dirk and Henk and at the

same fourth floor_corridor_as the room_of our friend Jeff Zucker. We had a well-attended_Intercity Colloquium, bi-weekly taking place alternatingly_at the institutes_in_Amsterdam_and Utrecht. Anne Troelstra,_Dick de Jongh, Roel de Vrijer_were regular participants,

together with visitors in_those years such as Walter van Stigt,_David Isles and Craig Smorynski, and_many more short or long_term visiting_friends and colleagues from abroad._As a junior_Ph.D-student under_supervision of Dirk_and Henk my (too) difficult assignment_was to assist_a group of newcoming students, including_Albert,_in digesting and_mastering_various_chapters of_Anne’s famous Springer_LNM_344, shortly_known_as ‘344’.



The encounter with 344 did_not_influence me as deeply as would have_been desirable, but in_my_subsequent development to a_theoretical computer scientist I did_greatly profit from the treatment in_344 of_important recursion_theory theorems such as the ones of Myhill-Shepherdson and Kreisel-Lacombe-Schoenfield. They_were instrumental in a later paper_(1982) by Jan Bergstra_and me_about_parametrized data types,_continuing_Jan’s well-known_series of papers together with John Tucker_from Swansea,_analyzing the theory of abstract data_types.



I used to drive_our_Utrecht group, Dirk, Henk, Jeff, Albert_in my small car to the_Amsterdam sessions of the Intercity_seminar,_and_dually, drive the Amsterdam participants,_Anne, Dick, Roel after the Utrecht_sessions back to_Utrecht Central Station. I remember Anne’s stimulating_comments,_when I had made good progress_with_my PhD-thesis, about term rewriting systems_and_lambda_calculus. I remember Anne as_a true scholar and a gentleman._He was an example, a role model for junior_logicians and computer_scientists. At the event of_his_emeritate,_I thanked him for his