Go backward to SubtypingGo up to TopGo forward to Denotational Semantics |

- Coercion rule
`pi`|- 2:`real``pi`|- 2+4.5:`realexp`

- Unicity of typing is lost:
`pi`|- 2+3:`intexp``pi`|- 2+3:`realexp`

- Minimal type of every expression:
`pi`|- U:`theta`_{1}`theta`<=_{1}`theta`, for all_{2}`pi`|- U:`theta`_{2}- Attach each tree node with minimal type!

- Minimal type may not exist:
`nonnegative`<=`int``nonpositive`<=`int`- 0:
`nonnegative`, 0:`nonpositive`

Author: Wolfgang Schreiner

Last Modification: May 14, 1998