Description: Variables in sentences of propositional calculus are encoded by appending a zero after the number of the variable. (Contributed by Thomas van Maaren, 21-Aug-2026)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | df-propvar | |- propvar = ( n e. NN |-> ( <" n "> ++ <" 0 "> ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 0 | cpropvar | |- propvar |
|
| 1 | vn | |- n |
|
| 2 | cn | |- NN |
|
| 3 | 1 | cv | |- n |
| 4 | 3 | cs1 | |- <" n "> |
| 5 | cconcat | |- ++ |
|
| 6 | cc0 | |- 0 |
|
| 7 | 6 | cs1 | |- <" 0 "> |
| 8 | 4 7 5 | co | |- ( <" n "> ++ <" 0 "> ) |
| 9 | 1 2 8 | cmpt | |- ( n e. NN |-> ( <" n "> ++ <" 0 "> ) ) |
| 10 | 0 9 | wceq | |- propvar = ( n e. NN |-> ( <" n "> ++ <" 0 "> ) ) |