| Original language | English |
|---|---|
| Pages (from-to) | 279-296 |
| Number of pages | 18 |
| Journal | Science of Computer Programming |
| Volume | 7 |
| Issue number | C |
| DOIs | |
| Publication status | Published (VoR) - 1986 |
Funding
I wish to thank Tony Hoare, Richard Bird and Phil Wadler for their helpful and encouraging comments on earlier drafts of this paper. I am also grateful to the referees for suggesting improvements. I acknowledge the financiar support of the British Science and Engineering Research Council.