Singular Manual: Type conversion and casting

| ### 3.5.5 Type conversion and casting #### Type conversion Assignments convert the type of the right-hand side to the type of the left-hand side of the assignment, if possible. Operators and functions which require certain types of operands can also implicitly convert the type of an expression. It is, for example, possible to multiply a polynomial by an integer because the integer is automatically converted to a polynomial. Type conversions do not act transitively. Possible conversions are:
1.
| `intvec` | ==> `intmat`
2. | `poly` | ==> `ideal`
3. | `bigint` | ==> `ideal`
4. | `int` | ==> `ideal`
5. | `intmat` | ==> `matrix`
6. | `ideal` | ==> `matrix`
7. | `module` | ==> `matrix`
8. | `number` | ==> `matrix`
9. | `poly` | ==> `matrix`
10. | `vector` | ==> `matrix`
11. | `bigint` | ==> `matrix`
12. | `int` | ==> `matrix`
13. | `intvec` | ==> `matrix`
14. | `ideal` | ==> `module`
15. | `matrix` | ==> `module`
16. | `vector` | ==> `module`
17. | `bigint` | ==> `number`
18. | `int` | ==> `number`
19. | `number` | ==> `poly`
20. | `bigint` | ==> `poly`
21. | `int` | ==> `poly`
22. | `list` | ==> `resolution`
23. | `poly` | ==> `vector` (p ==> p*`gen(1)`)
24. | `bigint` | ==> `vector`
25. | `int` | ==> `vector` (i ==> i*`gen(1)`)
26. | `int` | ==> `bigint`
27. | `int` | ==> `intvec`
28. | `string` | ==> `link`
29. | `resolution` | ==> `list`
30. | `intvec` | ==> `bigintvec`

#### Type casting

An expression can be casted to another type by using a type cast expression:
type `(` expression `)`.

Possible type casts are:

| to | from
| `bigint` | expression `int`, `number`, `poly`
| `bigintvec` | expression `int`, `bigint`
| `ideal` | expression lists of `int`, `number`, `poly`
| `ideal` | `int`, `matrix`, `module`, `number`, `poly`, `vector`
| `int` | `number`, `poly`
| `intvec` | expression lists of `int`, `intmat`, `bigintvec`
| `intmat` | `intvec` (see intmat type cast)
| `list` | expression lists of any type
| `matrix` | `module`, `ideal`, `vector`, `matrix`. There are two forms to convert something to a matrix: if `matrix(` expression `)` is used then the size of the matrix is determined by the size of expression. But `matrix(` expression `,` m `,` n `)` may also be used - the result is a 68#68matrix (see matrix type cast)
| `module` | expression lists of `int`, `number`, `poly`, `vector`
| `module` | `ideal`, `matrix`, `vector`
| `number` | `poly`
| `poly` | `int`, `number`
| `ring` | `list` (the inverse of `ringlist`)
| `string` | any type (see string type cast)

Example:

      ring r=0,x,(c,dp);
      number(3x);
    ==> 0
      number(poly(3));
    ==> 3
      ideal i=1,2,3,4,5,6;
      print(matrix(i));
    ==> 1,2,3,4,5,6
      print(matrix(i,3,2));
    ==> 1,2,
    ==> 3,4,
    ==> 5,6
      vector v=[1,2];
      print(matrix(v));
    ==> 1,
    ==> 2
      module(matrix(i,3,2));
    ==> _[1]=[1,3,5]
    ==> _[2]=[2,4,6]
      // generators are columns of a matrix

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